feat: 媒体库 blob 去重存储与品牌/注册等前端调整

新增：
- blob_store 二进制去重存储 + blob_dedup 测试

其它：
- 后端 settings/auth/media_library/upload/operations 服务与 handler 调整
- 前端品牌（BrandLockup/BrandCropModal/BrandSeoPanel）、注册、媒体库、分析详情页、Header/SiteChrome 等更新

backend/handler/operations.go

@@ -262,6 +262,10 @@ func (h *Handlers) SendEmailCode(c *gin.Context) {
 		return
 	}
 	wait, e := h.Ops.SendCode(req.Email, req.Purpose, c.ClientIP())
+	if errors.Is(e, service.ErrEmailRegistered) {
+		c.JSON(http.StatusBadRequest, gin.H{"error": e.Error()})
+		return
+	}
 	if !h.quotaResponse(c, wait, e) {
 		return
 	}

backend/handler/setting.go

@@ -57,6 +57,7 @@ type updateSettingsRequest struct {
 	BrandMark            *string               `json:"brand_mark"`
 	BrandLogoSize        *string               `json:"brand_logo_size"`
 	BrandLogoFit         *string               `json:"brand_logo_fit"`
+	BrandSloganVisible   *bool                 `json:"brand_slogan_visible"`
 	FooterLinks          *[]service.FooterLink `json:"footer_links"`
 
 	PointsCheckinBase     *int `json:"points_checkin_base"`
@@ -120,6 +121,7 @@ func settingsPayload(saved service.PublicSiteSettings) gin.H {
 		"brand_mark":             saved.BrandMark,
 		"brand_logo_size":        saved.BrandLogoSize,
 		"brand_logo_fit":         saved.BrandLogoFit,
+		"brand_slogan_visible":   saved.BrandSloganVisible,
 		"footer_links":           saved.FooterLinks,
 
 		"points_checkin_base":      saved.PointsCheckinBase,
@@ -160,6 +162,7 @@ func (req *updateSettingsRequest) hasAny() bool {
 		req.SiteWordmark != nil || req.SiteSlogan != nil || req.SiteKeywords != nil ||
 		req.LogoLightURL != nil || req.LogoDarkURL != nil || req.FaviconURL != nil ||
 		req.BrandMark != nil || req.BrandLogoSize != nil || req.BrandLogoFit != nil ||
+		req.BrandSloganVisible != nil ||
 		req.FooterLinks != nil ||
 		req.PointsCheckinBase != nil || req.PointsStreakEveryDays != nil || req.PointsStreakBonus != nil ||
 		req.PointsPostReward != nil || req.PointsPostDailyCap != nil ||
@@ -540,6 +543,12 @@ func (h *Handlers) UpdateSettings(c *gin.Context) {
 			return
 		}
 	}
+	if req.BrandSloganVisible != nil {
+		if err := h.Setting.SetBrandSloganVisible(*req.BrandSloganVisible); err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": "保存站点设置失败"})
+			return
+		}
+	}
 	if req.FooterLinks != nil {
 		if err := h.Setting.SetFooterLinks(*req.FooterLinks); err != nil {
 			if errors.Is(err, service.ErrInvalidSiteSetting) {

backend/model/db.go

@@ -56,7 +56,7 @@ func InitDB(dsn string) error {
 	}
 
 	if err := db.AutoMigrate(
-		&TemporaryUpload{}, &ModuleConfig{}, &SettingsAudit{}, &ActionCounter{}, &MailTask{}, &EmailChallenge{}, &StoredObject{},
+		&TemporaryUpload{}, &ModuleConfig{}, &SettingsAudit{}, &ActionCounter{}, &MailTask{}, &EmailChallenge{}, &StoredObject{}, &Blob{},
 		&User{}, &Board{}, &Post{}, &PostEditHistory{}, &Comment{}, &CommentEditHistory{}, &RefreshToken{}, &Like{}, &Favorite{}, &Follow{}, &Notification{}, &Checkin{},
 		&Announcement{}, &SitePage{}, &SiteSetting{}, &SiteDailyStats{}, &SiteDailyVisitor{}, &VisitEvent{}, &Attachment{}, &UserBoard{}, &LoginLog{},
 		&ChatRoom{}, &ChatRoomMember{}, &ChatMessage{},

backend/model/models.go

@@ -362,12 +362,13 @@ type PostContentUnlock struct {
 
 // PostAttachment 帖子文件附件（不走公开静态目录，经 API 鉴权下载）
 type PostAttachment struct {
-	ObjectID      string         `gorm:"size:64;index" json:"-"`
+	ObjectID      string         `gorm:"size:96;index" json:"-"`
 	ID            uint           `gorm:"primaryKey" json:"id"`
 	PostID        uint           `gorm:"index;not null;default:0" json:"post_id"` // 0=草稿未绑定
 	UserID        uint           `gorm:"index;not null" json:"user_id"`
-	Name          string         `gorm:"size:256;not null" json:"name"` // 原始文件名
-	StoredName    string         `gorm:"size:64;not null" json:"-"`     // 磁盘文件名
+	Name          string         `gorm:"size:256;not null" json:"name"`              // 原始文件名
+	StoredName    string         `gorm:"size:64;not null" json:"-"`                  // 磁盘文件名（blob 去重后即内容 hash）
+	BlobHash      string         `gorm:"size:64;not null;default:'';index" json:"-"` // 内容寻址 hash；空=历史文件，不走引用计数
 	MIME          string         `gorm:"size:128;not null;default:application/octet-stream" json:"mime"`
 	Size          int            `gorm:"not null;default:0" json:"size"`
 	PricePoints   int            `gorm:"not null;default:0" json:"price_points"` // 0=免费
@@ -666,13 +667,14 @@ const (
 	AttachmentSourceLibraryContent = "library_content" // 书库正文内容插图
 )
 
-// Attachment 用户上传的附件（当前仅头像，全部为 WebP）
+// Attachment 用户上传的附件（头像与帖子插图等公开图片）
 type Attachment struct {
 	ID        uint      `gorm:"primaryKey" json:"id"`
 	UserID    uint      `gorm:"index:idx_attachment_user_kind,priority:1;not null" json:"user_id"`
 	Kind      string    `gorm:"size:16;index:idx_attachment_user_kind,priority:2;not null" json:"kind"`
 	Source    string    `gorm:"size:24;not null;default:'post'" json:"source"`
 	URL       string    `gorm:"size:512;not null" json:"url"`
+	BlobHash  string    `gorm:"size:64;not null;default:'';index" json:"-"` // 内容寻址 hash；空=历史文件，不走引用计数
 	MIME      string    `gorm:"size:32;not null;default:image/webp" json:"mime"`
 	Size      int       `gorm:"not null;default:0" json:"size"` // 裁剪后文件字节数（大小限制以此为准）
 	Width     int       `gorm:"not null;default:0" json:"width"`
@@ -680,6 +682,20 @@ type Attachment struct {
 	CreatedAt time.Time `gorm:"index" json:"created_at"`
 }
 
+// Blob 内容寻址物理文件：对【最终存储字节】算 SHA-256，同内容多次上传共享一份底层存储，
+// 业务行（Attachment/PostAttachment 及未来的聊天文件消息）只引用 hash，按引用计数回收。
+// 公开（帖子插图/头像）与私有（付费附件、未来私聊文件）是两个互不可见的命名空间：
+// 同字节也各自存一份，避免私有文件借公开链接（/api/media/<id>）被越权读取。
+type Blob struct {
+	Hash      string    `gorm:"primaryKey;size:64" json:"-"` // 最终存储字节的 SHA-256 hex（图片为转码后的字节）
+	Public    bool      `gorm:"primaryKey" json:"-"`
+	RefCount  int64     `gorm:"not null;default:0" json:"-"`
+	Size      int       `gorm:"not null;default:0" json:"-"`
+	MIME      string    `gorm:"size:128;not null;default:''" json:"-"`
+	ObjectID  string    `gorm:"size:96;not null;default:''" json:"-"` // S3 后端的 StoredObject ID；本地后端为空
+	CreatedAt time.Time `json:"-"`
+}
+
 // UserBoard 板块管理员的板块授权（多对多；仅 role=board_admin 的行生效）
 type UserBoard struct {
 	ID        uint      `gorm:"primaryKey" json:"id"`

backend/model/operations.go

@@ -51,7 +51,7 @@ type EmailChallenge struct {
 
 // Every remote object pins the immutable configuration revision that wrote it.
 type StoredObject struct {
-	ID         string    `gorm:"primaryKey;size:64" json:"id"`
+	ID         string    `gorm:"primaryKey;size:96" json:"id"`
 	ConfigName string    `gorm:"size:64;index" json:"-"`
 	Key        string    `gorm:"size:512" json:"-"`
 	MIME       string    `gorm:"size:128" json:"-"`

backend/service/auth.go

@@ -107,10 +107,13 @@ var dummyPasswordHash, _ = bcrypt.GenerateFromPassword(
 	[]byte("j13-dummy-password-for-constant-timing"), bcrypt.DefaultCost)
 
 // Register 用户注册（事务 + 咨询锁，保证空库至多一名 owner）
+// 邮箱非空时全库唯一（忽略大小写）：后期支持邮箱登录，一邮箱只能对应一个账号
 func (s *AuthService) Register(username, email, password string) (*model.User, error) {
 	if err := NewOperations(s.db, nil).Filter("username", username, 0); err != nil {
 		return nil, err
 	}
+	// 邮箱统一小写归一化，避免大小写变体重复注册
+	email = strings.ToLower(strings.TrimSpace(email))
 
 	hashed, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
 	if err != nil {
@@ -130,6 +133,16 @@ func (s *AuthService) Register(username, email, password string) (*model.User, e
 		if count > 0 {
 			return errors.New("用户名已被使用")
 		}
+		// 邮箱唯一（忽略大小写，兜底防绕过；入口发码处已拦一次）
+		if email != "" {
+			var emailCount int64
+			if err := tx.Model(&model.User{}).Where("LOWER(email) = ?", email).Count(&emailCount).Error; err != nil {
+				return err
+			}
+			if emailCount > 0 {
+				return errors.New("该邮箱已被注册")
+			}
+		}
 		var n int64
 		if err := tx.Model(&model.User{}).Count(&n).Error; err != nil {
 			return err
@@ -681,14 +694,14 @@ func (s *AuthService) UpdateProfile(userID uint, nickname, email, signature stri
 	if nickCount > 0 {
 		return nil, errors.New("该昵称已被使用")
 	}
-	email = strings.TrimSpace(email)
+	email = strings.ToLower(strings.TrimSpace(email))
 	if email != "" {
 		if !strings.Contains(email, "@") || len(email) > 128 {
 			return nil, errors.New("邮箱格式不正确")
 		}
-		// 邮箱唯一性校验（排除自身）
+		// 邮箱唯一性校验（忽略大小写，排除自身），与注册口径一致
 		var count int64
-		s.db.Model(&model.User{}).Where("email = ? AND id <> ?", email, userID).Count(&count)
+		s.db.Model(&model.User{}).Where("LOWER(email) = ? AND id <> ?", email, userID).Count(&count)
 		if count > 0 {
 			return nil, errors.New("该邮箱已被使用")
 		}

backend/service/blob_dedup_test.go

@@ -0,0 +1,223 @@
+package service
+
+import (
+	"bytes"
+	"image"
+	"image/color"
+	"image/jpeg"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/freefire/jiang13-bbs/model"
+	webpenc "github.com/gen2brain/webp"
+	"github.com/glebarez/sqlite"
+	"gorm.io/gorm"
+)
+
+func newBlobTestDB(t *testing.T) *gorm.DB {
+	t.Helper()
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	if err := db.AutoMigrate(
+		&model.Blob{}, &model.Attachment{}, &model.PostAttachment{},
+		&model.User{}, &model.Post{},
+	); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	return db
+}
+
+func webpFixtureBytes() []byte {
+	src := image.NewRGBA(image.Rect(0, 0, 20, 10))
+	src.Set(0, 0, color.RGBA{10, 20, 30, 255})
+	var buf bytes.Buffer
+	_ = webpenc.Encode(&buf, src, webpenc.Options{Quality: ImageWebPQuality})
+	return buf.Bytes()
+}
+
+func TestSaveImageBlobDedupAndRefcount(t *testing.T) {
+	db := newBlobTestDB(t)
+	dir := t.TempDir()
+	s := NewUploadService(db, dir)
+	if err := s.EnsureDir(); err != nil {
+		t.Fatalf("ensure dir: %v", err)
+	}
+	data := webpFixtureBytes()
+
+	att1, err := s.SaveImage(1, bytes.NewReader(data), "post")
+	if err != nil {
+		t.Fatalf("SaveImage 1: %v", err)
+	}
+	att2, err := s.SaveImage(2, bytes.NewReader(data), "post")
+	if err != nil {
+		t.Fatalf("SaveImage 2: %v", err)
+	}
+	if att1.URL != att2.URL || att1.BlobHash == "" || att1.BlobHash != att2.BlobHash {
+		t.Fatalf("identical content should share url/hash: %q vs %q", att1.URL, att2.URL)
+	}
+
+	var blob model.Blob
+	if err := db.First(&blob, "hash = ? AND public = ?", att1.BlobHash, true).Error; err != nil {
+		t.Fatalf("load blob: %v", err)
+	}
+	if blob.RefCount != 2 {
+		t.Fatalf("refcount want 2, got %d", blob.RefCount)
+	}
+	blobPath := filepath.Join(dir, filepath.FromSlash(att1.URL[len("/uploads/"):]))
+	if fi, err := os.Stat(blobPath); err != nil || fi.IsDir() {
+		t.Fatalf("shared physical file missing: %v", err)
+	}
+
+	// 删一个引用：文件保留
+	if err := s.DeleteAttachment(1, att1.ID); err != nil {
+		t.Fatalf("DeleteAttachment 1: %v", err)
+	}
+	db.First(&blob, "hash = ? AND public = ?", att1.BlobHash, true)
+	if blob.RefCount != 1 {
+		t.Fatalf("refcount want 1, got %d", blob.RefCount)
+	}
+	if _, err := os.Stat(blobPath); err != nil {
+		t.Fatalf("blob file should survive while referenced: %v", err)
+	}
+
+	// 最后一个引用删除：文件与 blob 行一起回收
+	if err := s.DeleteAttachment(2, att2.ID); err != nil {
+		t.Fatalf("DeleteAttachment 2: %v", err)
+	}
+	if _, err := os.Stat(blobPath); !os.IsNotExist(err) {
+		t.Fatalf("blob file should be removed after last release, stat err=%v", err)
+	}
+	var n int64
+	db.Model(&model.Blob{}).Where("hash = ? AND public = ?", att1.BlobHash, true).Count(&n)
+	if n != 0 {
+		t.Fatalf("blob row should be gone, count=%d", n)
+	}
+}
+
+func TestSaveImageTranscodedJPEGDedup(t *testing.T) {
+	db := newBlobTestDB(t)
+	dir := t.TempDir()
+	s := NewUploadService(db, dir)
+	if err := s.EnsureDir(); err != nil {
+		t.Fatalf("ensure dir: %v", err)
+	}
+
+	src := image.NewRGBA(image.Rect(0, 0, 48, 36))
+	src.Set(1, 2, color.RGBA{200, 100, 50, 255})
+	var in bytes.Buffer
+	if err := jpeg.Encode(&in, src, nil); err != nil {
+		t.Fatalf("encode jpeg: %v", err)
+	}
+
+	att1, err := s.SaveImage(1, bytes.NewReader(in.Bytes()), "post")
+	if err != nil {
+		t.Fatalf("SaveImage 1: %v", err)
+	}
+	att2, err := s.SaveImage(1, bytes.NewReader(in.Bytes()), "post")
+	if err != nil {
+		t.Fatalf("SaveImage 2: %v", err)
+	}
+	// hash 必须对转码后的字节计算：同源 JPEG 两次上传应命中同一个 WebP blob
+	if att1.URL != att2.URL || att1.BlobHash != att2.BlobHash {
+		t.Fatalf("transcoded JPEG should dedup: %q(%s) vs %q(%s)", att1.URL, att1.BlobHash, att2.URL, att2.BlobHash)
+	}
+}
+
+func TestSaveDraftFileBlobDedupAndRefcount(t *testing.T) {
+	db := newBlobTestDB(t)
+	root := t.TempDir()
+	s := NewPostFileService(db, root)
+	if err := s.EnsureDir(); err != nil {
+		t.Fatalf("ensure dir: %v", err)
+	}
+	data := []byte("paid attachment content v1")
+
+	a1, err := s.SaveDraftFile(1, "report.pdf", bytes.NewReader(data), 50)
+	if err != nil {
+		t.Fatalf("SaveDraftFile 1: %v", err)
+	}
+	a2, err := s.SaveDraftFile(2, "another-name.pdf", bytes.NewReader(data), 0)
+	if err != nil {
+		t.Fatalf("SaveDraftFile 2: %v", err)
+	}
+	if a1.BlobHash == "" || a1.BlobHash != a2.BlobHash || a1.StoredName != a2.StoredName {
+		t.Fatalf("same bytes should share blob: %+v vs %+v", a1, a2)
+	}
+	// 原始文件名仍各自保留
+	if a1.Name != "report.pdf" || a2.Name != "another-name.pdf" {
+		t.Fatalf("original names not preserved: %q / %q", a1.Name, a2.Name)
+	}
+	blobPath := s.FilePath(a1)
+	if _, err := os.Stat(blobPath); err != nil {
+		t.Fatalf("shared private blob missing: %v", err)
+	}
+
+	var blob model.Blob
+	if err := db.First(&blob, "hash = ? AND public = ?", a1.BlobHash, false).Error; err != nil {
+		t.Fatalf("load private blob: %v", err)
+	}
+	if blob.RefCount != 2 {
+		t.Fatalf("refcount want 2, got %d", blob.RefCount)
+	}
+
+	if err := s.DeleteOwn(1, a1.ID); err != nil {
+		t.Fatalf("DeleteOwn 1: %v", err)
+	}
+	if _, err := os.Stat(blobPath); err != nil {
+		t.Fatalf("private blob should survive with one ref: %v", err)
+	}
+	if err := s.DeleteOwn(2, a2.ID); err != nil {
+		t.Fatalf("DeleteOwn 2: %v", err)
+	}
+	if _, err := os.Stat(blobPath); !os.IsNotExist(err) {
+		t.Fatalf("private blob should be removed after last release, stat err=%v", err)
+	}
+}
+
+func TestBlobPublicPrivateVisibilityIsolation(t *testing.T) {
+	db := newBlobTestDB(t)
+	root := t.TempDir()
+	img := NewUploadService(db, filepath.Join(root, "uploads"))
+	pf := NewPostFileService(db, filepath.Join(root, "private"))
+	if err := img.EnsureDir(); err != nil {
+		t.Fatalf("ensure upload dir: %v", err)
+	}
+	if err := pf.EnsureDir(); err != nil {
+		t.Fatalf("ensure private dir: %v", err)
+	}
+	data := webpFixtureBytes()
+
+	att, err := img.SaveImage(1, bytes.NewReader(data), "post")
+	if err != nil {
+		t.Fatalf("SaveImage: %v", err)
+	}
+	file, err := pf.SaveDraftFile(1, "x.webp", bytes.NewReader(data), 0)
+	if err != nil {
+		t.Fatalf("SaveDraftFile: %v", err)
+	}
+	if att.BlobHash != file.BlobHash {
+		t.Fatalf("test premise: same bytes should produce same hash")
+	}
+
+	// 同字节在公开/私有命名空间各持一条 blob，互不复用，防止越权读取
+	var pubs, privs int64
+	db.Model(&model.Blob{}).Where("hash = ? AND public = ?", att.BlobHash, true).Count(&pubs)
+	db.Model(&model.Blob{}).Where("hash = ? AND public = ?", att.BlobHash, false).Count(&privs)
+	if pubs != 1 || privs != 1 {
+		t.Fatalf("want separate public/private blobs, pubs=%d privs=%d", pubs, privs)
+	}
+	publicPath := filepath.Join(root, "uploads", filepath.FromSlash(att.URL[len("/uploads/"):]))
+	privatePath := pf.FilePath(file)
+	if publicPath == privatePath {
+		t.Fatal("public and private blob must not share a path")
+	}
+	if _, err := os.Stat(publicPath); err != nil {
+		t.Fatalf("public blob missing: %v", err)
+	}
+	if _, err := os.Stat(privatePath); err != nil {
+		t.Fatalf("private blob missing: %v", err)
+	}
+}

backend/service/blob_store.go

@@ -0,0 +1,132 @@
+package service
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/freefire/jiang13-bbs/model"
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+)
+
+// 内容寻址存储（content-addressed storage）：
+// 物理文件按【最终存储字节】的 SHA-256 命名，业务行只引用 hash 并各持一份引用计数；
+// 同内容重复上传不再重复落盘/传输，最后一个引用删除时才回收物理文件。
+// 公开与私有是独立命名空间（见 model.Blob 注释）。
+
+// sha256Hex 计算字节的 SHA-256 hex
+func sha256Hex(data []byte) string {
+	sum := sha256.Sum256(data)
+	return hex.EncodeToString(sum[:])
+}
+
+// hashFile 计算文件内容的 SHA-256 hex，整文件流式读取不进内存
+func hashFile(path string) (string, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+	h := sha256.New()
+	if _, err := io.Copy(h, f); err != nil {
+		return "", err
+	}
+	return hex.EncodeToString(h.Sum(nil)), nil
+}
+
+// acquireBlobRef 登记一次 blob 引用：行不存在则创建（计数=1），已存在则计数+1。
+// 并发下靠 (hash, public) 主键冲突重试，保证不丢计数。
+func acquireBlobRef(db *gorm.DB, hash string, public bool, size int, mimeType, objectID string) error {
+	for {
+		var b model.Blob
+		err := db.Where("hash = ? AND public = ?", hash, public).First(&b).Error
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			b = model.Blob{
+				Hash:     hash,
+				Public:   public,
+				RefCount: 1,
+				Size:     size,
+				MIME:     mimeType,
+				ObjectID: objectID,
+			}
+			if err := db.Create(&b).Error; err != nil {
+				if isUniqueConflict(err) {
+					continue // 并发首建：改为走计数+1
+				}
+				return err
+			}
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+		return db.Model(&model.Blob{}).
+			Where("hash = ? AND public = ?", hash, public).
+			UpdateColumn("ref_count", gorm.Expr("ref_count + 1")).Error
+	}
+}
+
+// releaseBlobRef 释放一次 blob 引用。计数归零时删行并返回 last=true 与该行快照
+// （快照里的 ObjectID/Hash 供调用方回收物理对象）。行不存在视为幂等成功。
+func releaseBlobRef(db *gorm.DB, hash string, public bool) (model.Blob, bool, error) {
+	var removed model.Blob
+	var last bool
+	err := db.Transaction(func(tx *gorm.DB) error {
+		var b model.Blob
+		// 行锁：postgres 下 FOR UPDATE 串行化同 blob 的并发释放；sqlite 写事务天然串行
+		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
+			First(&b, "hash = ? AND public = ?", hash, public).Error; err != nil {
+			if errors.Is(err, gorm.ErrRecordNotFound) {
+				return nil
+			}
+			return err
+		}
+		if b.RefCount <= 1 {
+			result := tx.Where("hash = ? AND public = ? AND ref_count <= 1", hash, public).Delete(&model.Blob{})
+			if result.Error != nil {
+				return result.Error
+			}
+			if result.RowsAffected > 0 {
+				removed = b
+				last = true
+			}
+			return nil
+		}
+		return tx.Model(&model.Blob{}).
+			Where("hash = ? AND public = ?", hash, public).
+			UpdateColumn("ref_count", b.RefCount-1).Error
+	})
+	if err != nil {
+		return model.Blob{}, false, err
+	}
+	return removed, last, nil
+}
+
+// placeLocalBlob 把临时文件原子放到内容寻址目标路径：
+// 目标已存在说明同内容已落盘（字节必然一致），直接丢弃源文件；否则整体 rename。
+// src 与 dst 同一路径时不做操作。
+func placeLocalBlob(src, dst string) error {
+	if abs, err := filepath.Abs(src); err == nil {
+		if dstAbs, err := filepath.Abs(dst); err == nil && abs == dstAbs {
+			return nil
+		}
+	}
+	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
+		return err
+	}
+	if _, err := os.Stat(dst); err == nil {
+		if src != dst {
+			_ = os.Remove(src)
+		}
+		return nil
+	}
+	if err := os.Rename(src, dst); err != nil {
+		_ = os.Remove(src)
+		return err
+	}
+	return nil
+}

backend/service/brand.go

@@ -9,16 +9,17 @@ import (
 
 // 站点品牌与页脚（公开设置，缺省为空）
 const (
-	SettingKeySiteWordmark  = "site_wordmark"
-	SettingKeySiteSlogan    = "site_slogan"
-	SettingKeySiteKeywords  = "site_keywords"
-	SettingKeyLogoLightURL  = "logo_light_url"
-	SettingKeyLogoDarkURL   = "logo_dark_url"
-	SettingKeyFaviconURL    = "favicon_url"
-	SettingKeyFooterLinks   = "footer_links"
-	SettingKeyBrandMark     = "brand_mark"
-	SettingKeyBrandLogoSize = "brand_logo_size"
-	SettingKeyBrandLogoFit  = "brand_logo_fit"
+	SettingKeySiteWordmark       = "site_wordmark"
+	SettingKeySiteSlogan         = "site_slogan"
+	SettingKeySiteKeywords       = "site_keywords"
+	SettingKeyLogoLightURL       = "logo_light_url"
+	SettingKeyLogoDarkURL        = "logo_dark_url"
+	SettingKeyFaviconURL         = "favicon_url"
+	SettingKeyFooterLinks        = "footer_links"
+	SettingKeyBrandMark          = "brand_mark"
+	SettingKeyBrandLogoSize      = "brand_logo_size"
+	SettingKeyBrandLogoFit       = "brand_logo_fit"
+	SettingKeyBrandSloganVisible = "brand_slogan_visible"
 
 	BrandSlotLight   = "logo_light"
 	BrandSlotDark    = "logo_dark"
@@ -43,6 +44,8 @@ const (
 	BrandLogoSize3x1 = "3x1"
 	BrandLogoSize4x1 = "4x1"
 	BrandLogoSize169 = "16x9"
+	// BrandLogoSizeAuto 原图比例：自由裁剪，页眉图槽按图片原始比例自适应宽度
+	BrandLogoSizeAuto = "auto"
 
 	BrandLogoFitCover   = "cover"
 	BrandLogoFitContain = "contain"
@@ -114,7 +117,7 @@ func NormalizeBrandLogoSize(raw string) (string, bool) {
 	switch strings.TrimSpace(raw) {
 	case "", BrandLogoSizeSQ:
 		return BrandLogoSizeSQ, true
-	case BrandLogoSize2x1, BrandLogoSize3x1, BrandLogoSize4x1, BrandLogoSize169:
+	case BrandLogoSize2x1, BrandLogoSize3x1, BrandLogoSize4x1, BrandLogoSize169, BrandLogoSizeAuto:
 		return strings.TrimSpace(raw), true
 	default:
 		return "", false
@@ -367,6 +370,15 @@ func (s *SettingService) fillBrand(out *PublicSiteSettings) error {
 			out.BrandLogoFit = f
 		}
 	}
+	sv, found, err := s.getValue(SettingKeyBrandSloganVisible)
+	if err != nil {
+		return err
+	}
+	if found {
+		out.BrandSloganVisible = sv == "true"
+	} else {
+		out.BrandSloganVisible = true
+	}
 	rawLinks, found, err := s.getValue(SettingKeyFooterLinks)
 	if err != nil {
 		return err
@@ -483,6 +495,14 @@ func (s *SettingService) SetBrandLogoFit(raw string) error {
 	return s.putValue(SettingKeyBrandLogoFit, v)
 }
 
+// SetBrandSloganVisible 控制标语是否在页眉显示；true 为缺省值，存库时删 key 以保持精简。
+func (s *SettingService) SetBrandSloganVisible(visible bool) error {
+	if visible {
+		return s.deleteKey(SettingKeyBrandSloganVisible)
+	}
+	return s.putValue(SettingKeyBrandSloganVisible, "false")
+}
+
 func (s *SettingService) setBrandURL(key, slot, url string) error {
 	u, ok := NormalizeBrandURL(slot, url)
 	if !ok {

backend/service/media_library.go

@@ -64,6 +64,7 @@ type MediaLibraryItem struct {
 	Height       int        `json:"height"`
 	Uploader     string     `json:"uploader,omitempty"` // 上传者昵称（取自附件记录，无记录为空）
 	UploadedAt   *time.Time `json:"uploaded_at,omitempty"`
+	RefCount     int        `json:"ref_count,omitempty"`    // 引用计数（>1 表示内容相同的重复上传共享此文件）
 	SourceURL    string     `json:"source_url,omitempty"`   // 来源回链（帖子/评论锚点/用户主页）
 	SourceLabel  string     `json:"source_label,omitempty"` // 来源描述（如：帖子《…》下的评论）
 }
@@ -91,13 +92,29 @@ func (s *UploadService) AdminMediaLibrary() ([]MediaLibraryItem, map[string]int,
 		Scan(&rows).Error; err != nil {
 		return nil, nil, err
 	}
-	metaByURL := make(map[string]attMeta, len(rows))
-	// 远程存储对象（/api/media/）不在磁盘上，直接作为条目加入
-	items := make([]MediaLibraryItem, 0, len(rows))
+	// 同 URL 多条记录（内容寻址去重后，重复上传共享同一文件）：
+	// 上传者/时间取最早一条，计数即该文件的引用次数
+	type urlMeta struct {
+		meta  attMeta
+		count int
+	}
+	agg := make(map[string]*urlMeta, len(rows))
 	for _, r := range rows {
-		metaByURL[r.URL] = r // 本地文件在磁盘扫描时按 URL 合并元数据
-		if !strings.HasPrefix(r.URL, "/api/media/") {
-			continue
+		if a, ok := agg[r.URL]; ok {
+			a.count++
+			if r.CreatedAt.Before(a.meta.CreatedAt) {
+				a.meta = r
+			}
+		} else {
+			agg[r.URL] = &urlMeta{meta: r, count: 1}
+		}
+	}
+	// 远程存储对象（/api/media/）不在磁盘上，按 URL 去重后直接作为条目加入
+	items := make([]MediaLibraryItem, 0, len(agg))
+	for url, a := range agg {
+		r := a.meta
+		if !strings.HasPrefix(url, "/api/media/") {
+			continue // 本地文件在磁盘扫描时按 URL 合并元数据
 		}
 		if r.Kind != model.AttachmentKindImage && r.Kind != model.AttachmentKindAvatar {
 			continue // 未知 kind 不进媒体库
@@ -109,10 +126,10 @@ func (s *UploadService) AdminMediaLibrary() ([]MediaLibraryItem, map[string]int,
 		catKey, catName := mediaCategoryForAttachment(r.Kind, r.Source)
 		ca := r.CreatedAt
 		items = append(items, MediaLibraryItem{
-			URL: r.URL, Category: catKey, CategoryName: catName,
-			Name: strings.TrimPrefix(r.URL, "/api/media/"), MIME: r.MIME,
+			URL: url, Category: catKey, CategoryName: catName,
+			Name: strings.TrimPrefix(url, "/api/media/"), MIME: r.MIME,
 			Size: int64(r.Size), Width: r.Width, Height: r.Height,
-			Uploader: uploader, UploadedAt: &ca,
+			Uploader: uploader, UploadedAt: &ca, RefCount: a.count,
 		})
 	}
 
@@ -152,8 +169,9 @@ func (s *UploadService) AdminMediaLibrary() ([]MediaLibraryItem, map[string]int,
 				mt := info.ModTime()
 				item.UploadedAt = &mt
 			}
-			if m, ok := metaByURL[url]; ok {
+			if a, ok := agg[url]; ok {
 				// 附件记录有上传者与准确创建时间，覆盖磁盘信息
+				m := a.meta
 				uploader := m.Nickname
 				if uploader == "" {
 					uploader = m.Username
@@ -161,6 +179,7 @@ func (s *UploadService) AdminMediaLibrary() ([]MediaLibraryItem, map[string]int,
 				ca := m.CreatedAt
 				item.Uploader = uploader
 				item.UploadedAt = &ca
+				item.RefCount = a.count
 				if m.Size > 0 {
 					item.Size = int64(m.Size)
 				}

backend/service/media_library_test.go

@@ -25,7 +25,7 @@ func newMediaLibraryService(t *testing.T) (*UploadService, string) {
 	if err != nil {
 		t.Fatalf("open sqlite: %v", err)
 	}
-	if err := db.AutoMigrate(&model.Attachment{}, &model.User{}, &model.Post{}, &model.Comment{}); err != nil {
+	if err := db.AutoMigrate(&model.Attachment{}, &model.Blob{}, &model.User{}, &model.Post{}, &model.Comment{}); err != nil {
 		t.Fatalf("migrate: %v", err)
 	}
 	dir := t.TempDir()
@@ -315,6 +315,82 @@ func TestAdminMediaLibraryBookCategory(t *testing.T) {
 	}
 }
 
+func TestAdminMediaLibraryDedupAggregation(t *testing.T) {
+	s, dir := newMediaLibraryService(t)
+
+	writeMediaFile(t, dir, "images/dup.webp", []byte("fake-webp-bytes"))
+
+	mkUser := func(username, nickname string) model.User {
+		if err := s.db.Create(&model.User{Username: username, Nickname: nickname}).Error; err != nil {
+			t.Fatalf("create user: %v", err)
+		}
+		var u model.User
+		if err := s.db.Where("username = ?", username).First(&u).Error; err != nil {
+			t.Fatalf("load user: %v", err)
+		}
+		return u
+	}
+	alice := mkUser("alice", "爱丽丝")
+	bob := mkUser("bob", "阿Bob")
+
+	early := time.Date(2026, 9, 1, 10, 0, 0, 0, time.UTC)
+	late := early.Add(2 * time.Hour)
+
+	// 同一张图被两人先后上传（内容寻址去重后共享同一文件/对象）
+	mkAtt := func(u model.User, url string, at time.Time) {
+		if err := s.db.Create(&model.Attachment{
+			UserID: u.ID, Kind: model.AttachmentKindImage,
+			URL: url, MIME: "image/webp",
+			Size: 100, Width: 10, Height: 10, CreatedAt: at,
+		}).Error; err != nil {
+			t.Fatalf("create attachment %s: %v", url, err)
+		}
+	}
+	mkAtt(alice, "/uploads/images/dup.webp", early)
+	mkAtt(bob, "/uploads/images/dup.webp", late)
+	mkAtt(bob, "/api/media/rdup", early)
+	mkAtt(alice, "/api/media/rdup", late)
+
+	items, _, err := s.AdminMediaLibrary()
+	if err != nil {
+		t.Fatalf("AdminMediaLibrary: %v", err)
+	}
+
+	countByURL := map[string]int{}
+	byURL := map[string]MediaLibraryItem{}
+	for _, it := range items {
+		countByURL[it.URL]++
+		byURL[it.URL] = it
+	}
+
+	// 本地去重文件：单个条目，上传者/时间取最早上传的爱丽丝，引用计数 2
+	local, ok := byURL["/uploads/images/dup.webp"]
+	if !ok {
+		t.Fatal("dedup local file missing")
+	}
+	if countByURL["/uploads/images/dup.webp"] != 1 {
+		t.Fatal("dedup local file should appear exactly once")
+	}
+	if local.Uploader != "爱丽丝" || local.RefCount != 2 {
+		t.Fatalf("local dedup meta wrong: %+v", local)
+	}
+	if local.UploadedAt == nil || !local.UploadedAt.Equal(early) {
+		t.Fatalf("local dedup time should be earliest upload, got %v", local.UploadedAt)
+	}
+
+	// 远程对象同 URL 两条记录：也只出一个条目，取最早的 bob
+	remote, ok := byURL["/api/media/rdup"]
+	if !ok {
+		t.Fatal("dedup remote object missing")
+	}
+	if countByURL["/api/media/rdup"] != 1 {
+		t.Fatal("dedup remote object should appear exactly once")
+	}
+	if remote.Uploader != "阿Bob" || remote.RefCount != 2 {
+		t.Fatalf("remote dedup meta wrong: %+v", remote)
+	}
+}
+
 func TestMediaThumb(t *testing.T) {
 	s, dir := newMediaLibraryService(t)
 

backend/service/operations_mail.go

@@ -24,6 +24,9 @@ import (
 
 type mailPayload struct{ To, Subject, Body string }
 
+// ErrEmailRegistered 注册发码时邮箱已被占用，handler 据此返回 400 业务提示
+var ErrEmailRegistered = errors.New("该邮箱已被注册，请直接登录")
+
 func (o *Operations) smtp(ctx context.Context, c MailConfig, p *mailPayload, id string) error {
 	password, e := o.open(c.Password, "mail:password")
 	if e != nil {
@@ -392,6 +395,16 @@ func (o *Operations) SendCode(email, purpose, ip string) (int, error) {
 			return 0, nil
 		}
 	}
+	if purpose == "register" {
+		// 入口拦截：邮箱已被占用则不发码，省一次邮件资源，也给用户明确提示
+		var n int64
+		if e = o.db.Model(&model.User{}).Where("LOWER(email) = ?", email).Count(&n).Error; e != nil {
+			return 0, e
+		}
+		if n > 0 {
+			return 0, ErrEmailRegistered
+		}
+	}
 	code := randomCode()
 	hash := counterKey(email + ":" + purpose + ":" + code)
 	e = o.db.Transaction(func(tx *gorm.DB) error {

backend/service/operations_storage.go

@@ -16,6 +16,8 @@ import (
 	"path/filepath"
 	"strings"
 	"time"
+
+	"gorm.io/gorm"
 )
 
 func (o *Operations) s3(c StorageConfig) (*minio.Client, error) {
@@ -137,6 +139,65 @@ func (o *Operations) StoreFile(path, mimeType string, public bool) (string, erro
 	}
 	return id, nil
 }
+
+// blobObjectID 内容寻址对象的稳定 ID：公开/私有加不同前缀，同字节也不共享可见性。
+func blobObjectID(hash string, public bool) string {
+	if public {
+		return "pub_" + hash
+	}
+	return "prv_" + hash
+}
+
+// StoreFileHashed 按内容 hash 幂等上传：同一 (hash, public) 只存一份，重复上传跳过传输。
+// 本地后端返回空 ID（文件留在本地 blob 目录，由调用方做引用计数）。
+func (o *Operations) StoreFileHashed(path, mimeType string, public bool, hash string) (string, error) {
+	v, version, e := o.read(o.db, "storage")
+	if e != nil {
+		return "", errors.New("读取存储配置失败")
+	}
+	c := *v.(*StorageConfig)
+	if c.Backend == "local" {
+		return "", nil
+	}
+	id := blobObjectID(hash, public)
+	// hash 相同字节必然相同：对象已存在时直接复用，省掉整次上传
+	var existing model.StoredObject
+	if e := o.db.First(&existing, "id = ?", id).Error; e == nil {
+		return id, nil
+	} else if !errors.Is(e, gorm.ErrRecordNotFound) {
+		return "", e
+	}
+	client, e := o.s3(c)
+	if e != nil {
+		return "", e
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+	f, e := os.Open(path)
+	if e != nil {
+		return "", e
+	}
+	stat, e := f.Stat()
+	if e != nil {
+		_ = f.Close()
+		return "", e
+	}
+	key := c.Prefix + "objects/" + id
+	if _, e = client.PutObject(ctx, c.Bucket, key, f, stat.Size(), minio.PutObjectOptions{ContentType: mimeType, DisableMultipart: true}); e != nil {
+		_ = f.Close()
+		return "", errors.New("上传到 S3 失败，当前目标未自动切换")
+	}
+	_ = f.Close()
+	obj := model.StoredObject{ID: id, ConfigName: fmt.Sprintf("storage-%d", version), Key: key, MIME: mimeType, Public: public}
+	if e = o.db.Create(&obj).Error; e != nil {
+		if isUniqueConflict(e) { // 并发：另一请求已写入同内容对象，直接复用
+			return id, nil
+		}
+		_ = client.RemoveObject(ctx, c.Bucket, key, minio.RemoveObjectOptions{})
+		return "", errors.New("保存文件记录失败")
+	}
+	return id, nil
+}
 func (o *Operations) OpenObject(ctx context.Context, id string, requirePublic bool) (io.ReadCloser, string, error) {
 	var obj model.StoredObject
 	if e := o.db.First(&obj, "id = ?", id).Error; e != nil {

backend/service/post_file.go

@@ -2,10 +2,12 @@ package service
 
 import (
 	"crypto/rand"
+	"crypto/sha256"
 	"encoding/hex"
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"os"
 	"path/filepath"
 	"unicode/utf8"
@@ -145,8 +147,9 @@ func (s *PostFileService) SaveDraftFile(userID uint, originalName string, src io
 	if err != nil {
 		return nil, err
 	}
-	// LimitReader 多读 1 字节以区分「刚好上限」与「超限」
-	written, copyErr := io.Copy(f, io.LimitReader(src, maxB+1))
+	// LimitReader 多读 1 字节以区分「刚好上限」与「超限」；落盘同时计算内容 hash
+	hasher := sha256.New()
+	written, copyErr := io.Copy(io.MultiWriter(f, hasher), io.LimitReader(src, maxB+1))
 	_ = f.Close()
 	if copyErr != nil {
 		_ = os.Remove(tmp)
@@ -167,28 +170,45 @@ func (s *PostFileService) SaveDraftFile(userID uint, originalName string, src io
 		return nil, err
 	}
 
-	att := &model.PostAttachment{
-		PostID:      0,
-		UserID:      userID,
-		Name:        name,
-		StoredName:  stored,
-		MIME:        mimeType,
-		Size:        int(written),
-		PricePoints: pricePoints,
-	}
+	// 内容寻址：私有 blob 以 hash 命名（不带扩展名，下载时以 att.MIME + 原文件名下发）
+	hash := hex.EncodeToString(hasher.Sum(nil))
+	final := absPath(s.dir, hash)
+	var objectID string
 	if s.ops != nil {
-		id, e := s.ops.StoreFile(full, att.MIME, false)
+		id, e := s.ops.StoreFileHashed(full, mimeType, false, hash)
 		if e != nil {
 			_ = os.Remove(full)
 			return nil, e
 		}
-		att.ObjectID = id
+		objectID = id
 		if id != "" {
 			_ = os.Remove(full)
 		}
 	}
-	if err := s.db.Create(att).Error; err != nil {
-		_ = os.Remove(full)
+	if objectID == "" {
+		if e := placeLocalBlob(full, final); e != nil {
+			return nil, e
+		}
+	}
+
+	att := &model.PostAttachment{
+		PostID:      0,
+		UserID:      userID,
+		Name:        name,
+		StoredName:  hash,
+		BlobHash:    hash,
+		ObjectID:    objectID,
+		MIME:        mimeType,
+		Size:        int(written),
+		PricePoints: pricePoints,
+	}
+	if err := s.db.Transaction(func(tx *gorm.DB) error {
+		if e := acquireBlobRef(tx, hash, false, int(written), mimeType, objectID); e != nil {
+			return e
+		}
+		return tx.Create(att).Error
+	}); err != nil {
+		s.releasePostBlobBestEffort(hash)
 		return nil, err
 	}
 	return att, nil
@@ -283,14 +303,51 @@ func (s *PostFileService) DeleteOwn(userID, attID uint) error {
 	if att.UserID != userID {
 		return ErrAttachmentForbidden
 	}
-	path := absPath(s.dir, att.StoredName)
 	if err := s.db.Delete(&att).Error; err != nil {
 		return err
 	}
+	if att.BlobHash != "" {
+		return s.releasePostBlob(&att)
+	}
 	if s.ops != nil && att.ObjectID != "" {
 		return s.ops.RemoveObject(att.ObjectID)
 	}
-	_ = os.Remove(path)
+	_ = os.Remove(absPath(s.dir, att.StoredName))
+	return nil
+}
+
+// releasePostBlob 私有附件 blob 引用计数-1；最后一个引用删除时回收物理文件
+func (s *PostFileService) releasePostBlob(att *model.PostAttachment) error {
+	b, last, err := releaseBlobRef(s.db, att.BlobHash, false)
+	if err != nil || !last {
+		return err
+	}
+	return s.removePrivateBlobObject(b)
+}
+
+// releasePostBlobBestEffort 附件记录落库失败时回滚刚加的引用，错误只记日志
+func (s *PostFileService) releasePostBlobBestEffort(hash string) {
+	b, last, err := releaseBlobRef(s.db, hash, false)
+	if err != nil {
+		log.Printf("[post-file] 回滚 blob 引用失败 hash=%s: %v", hash, err)
+		return
+	}
+	if !last {
+		return
+	}
+	if err := s.removePrivateBlobObject(b); err != nil {
+		log.Printf("[post-file] 回滚 blob 物理文件失败 hash=%s: %v", hash, err)
+	}
+}
+
+// removePrivateBlobObject 引用归零后的物理回收（私有 blob 文件名即 hash，无扩展名）
+func (s *PostFileService) removePrivateBlobObject(b model.Blob) error {
+	if b.ObjectID != "" && s.ops != nil {
+		return s.ops.RemoveObject(b.ObjectID)
+	}
+	if err := os.Remove(absPath(s.dir, b.Hash)); err != nil && !os.IsNotExist(err) {
+		log.Printf("[post-file] 删除 blob 文件失败 hash=%s: %v", b.Hash, err)
+	}
 	return nil
 }
 

backend/service/setting.go

@@ -202,6 +202,7 @@ type PublicSiteSettings struct {
 	BrandMark            string       `json:"brand_mark"`
 	BrandLogoSize        string       `json:"brand_logo_size"`
 	BrandLogoFit         string       `json:"brand_logo_fit"`
+	BrandSloganVisible   bool         `json:"brand_slogan_visible"`
 	FooterLinks          []FooterLink `json:"footer_links"`
 
 	// 积分增长规则（经济规则公开透明，签到卡等可直出）

backend/service/upload.go

@@ -113,46 +113,57 @@ func (s *UploadService) SaveAvatar(userID uint, data []byte) (*model.Attachment,
 		return nil, errors.New("头像尺寸需在 64~512px 之间")
 	}
 
-	nameBytes := make([]byte, 16)
-	if _, err := rand.Read(nameBytes); err != nil {
-		return nil, err
-	}
-	filename := hex.EncodeToString(nameBytes) + ".webp"
+	hash := sha256Hex(data)
+	filename := hash + ".webp"
 	fullPath := filepath.Join(s.dir, "avatars", filename)
-	if err := os.WriteFile(fullPath, data, 0o644); err != nil {
-		return nil, err
+	url := "/uploads/avatars/" + filename
+	var objectID string
+	writeLocal := func() error {
+		if _, err := os.Stat(fullPath); err == nil {
+			return nil // 同内容头像已落盘，字节必然一致，无需重写
+		}
+		return os.WriteFile(fullPath, data, 0o644)
 	}
-
-	att := &model.Attachment{
-		UserID: userID,
-		Kind:   model.AttachmentKindAvatar,
-		URL:    "/uploads/avatars/" + filename,
-		MIME:   "image/webp",
-		Size:   len(data),
-		Width:  cfg.Width,
-		Height: cfg.Height,
-	}
-
 	if s.ops != nil {
-		id, e := s.ops.StoreFile(fullPath, att.MIME, true)
+		if err := writeLocal(); err != nil {
+			return nil, err
+		}
+		id, e := s.ops.StoreFileHashed(fullPath, "image/webp", true, hash)
 		if e != nil {
 			_ = os.Remove(fullPath)
 			return nil, e
 		}
+		objectID = id
 		if id != "" {
-			att.URL = "/api/media/" + id
+			url = "/api/media/" + id
 			_ = os.Remove(fullPath)
 		}
+	} else if err := writeLocal(); err != nil {
+		return nil, err
 	}
-	// 附件记录与用户头像更新在同一事务内完成
+
+	att := &model.Attachment{
+		UserID:   userID,
+		Kind:     model.AttachmentKindAvatar,
+		URL:      url,
+		BlobHash: hash,
+		MIME:     "image/webp",
+		Size:     len(data),
+		Width:    cfg.Width,
+		Height:   cfg.Height,
+	}
+	// 附件记录、blob 引用与用户头像更新在同一事务内完成
 	err = s.db.Transaction(func(tx *gorm.DB) error {
+		if err := acquireBlobRef(tx, hash, true, len(data), "image/webp", objectID); err != nil {
+			return err
+		}
 		if err := tx.Create(att).Error; err != nil {
 			return err
 		}
 		return tx.Model(&model.User{}).Where("id = ?", userID).Update("avatar", att.URL).Error
 	})
 	if err != nil {
-		_ = os.Remove(fullPath) // DB 失败时清理已落盘文件
+		s.releaseBlobBestEffort(hash, true, "/uploads/avatars/"+filename)
 		return nil, err
 	}
 	return att, nil
@@ -351,29 +362,51 @@ func (s *UploadService) SaveImage(userID uint, src io.Reader, source string) (*m
 		}
 	}
 
-	att := &model.Attachment{
-		UserID: userID,
-		Kind:   model.AttachmentKindImage,
-		Source: normalizeImageSource(source),
-		URL:    "/uploads/images/" + storeName,
-		MIME:   storeMime,
-		Size:   int(storeSize),
-		Width:  w,
-		Height: h,
+	// 对最终存储字节做内容寻址（JPEG/PNG 已在上面转成 WebP，同图重复上传才能命中）
+	hash, err := hashFile(storePath)
+	if err != nil {
+		_ = os.Remove(storePath)
+		return nil, err
 	}
+	finalName := hash + strings.ToLower(filepath.Ext(storeName))
+	url := "/uploads/images/" + finalName
+	var objectID string
 	if s.ops != nil {
-		id, e := s.ops.StoreFile(storePath, att.MIME, true)
+		id, e := s.ops.StoreFileHashed(storePath, storeMime, true, hash)
 		if e != nil {
 			_ = os.Remove(storePath)
 			return nil, e
 		}
+		objectID = id
 		if id != "" {
-			att.URL = "/api/media/" + id
+			// 远程后端：以对象 ID 为访问地址，本地临时副本回收
+			url = "/api/media/" + id
 			_ = os.Remove(storePath)
+		} else if e := placeLocalBlob(storePath, filepath.Join(s.dir, "images", finalName)); e != nil {
+			return nil, e
 		}
+	} else if e := placeLocalBlob(storePath, filepath.Join(s.dir, "images", finalName)); e != nil {
+		return nil, e
 	}
-	if err := s.db.Create(att).Error; err != nil {
-		_ = os.Remove(storePath)
+
+	att := &model.Attachment{
+		UserID:   userID,
+		Kind:     model.AttachmentKindImage,
+		Source:   normalizeImageSource(source),
+		URL:      url,
+		BlobHash: hash,
+		MIME:     storeMime,
+		Size:     int(storeSize),
+		Width:    w,
+		Height:   h,
+	}
+	if err := s.db.Transaction(func(tx *gorm.DB) error {
+		if err := acquireBlobRef(tx, hash, true, int(storeSize), storeMime, objectID); err != nil {
+			return err
+		}
+		return tx.Create(att).Error
+	}); err != nil {
+		s.releaseBlobBestEffort(hash, true, url)
 		return nil, err
 	}
 	return att, nil
@@ -722,6 +755,10 @@ func (s *UploadService) DeleteAttachment(userID, attachmentID uint) error {
 		return err
 	}
 
+	if att.BlobHash != "" {
+		return s.releaseAttachmentBlob(&att)
+	}
+
 	if s.ops != nil && strings.HasPrefix(att.URL, "/api/media/") {
 		if e := s.ops.RemoveObject(RemoteObjectID(att.URL)); e != nil {
 			return errors.New("记录已删除，远程文件清理未完成，请联系管理员")
@@ -736,4 +773,47 @@ func (s *UploadService) DeleteAttachment(userID, attachmentID uint) error {
 	return nil
 }
 
+// releaseAttachmentBlob 公开图片 blob 引用计数-1；最后一个引用删除时回收物理文件
+func (s *UploadService) releaseAttachmentBlob(att *model.Attachment) error {
+	b, last, err := releaseBlobRef(s.db, att.BlobHash, true)
+	if err != nil || !last {
+		return err
+	}
+	return s.removePublicBlobObject(b, att.URL)
+}
+
+// releaseBlobBestEffort 业务记录落库失败时回滚刚加的引用，错误只记日志
+func (s *UploadService) releaseBlobBestEffort(hash string, public bool, localURL string) {
+	b, last, err := releaseBlobRef(s.db, hash, public)
+	if err != nil {
+		log.Printf("[upload] 回滚 blob 引用失败 hash=%s: %v", hash, err)
+		return
+	}
+	if !last {
+		return
+	}
+	if err := s.removePublicBlobObject(b, localURL); err != nil {
+		log.Printf("[upload] 回滚 blob 物理文件失败 hash=%s: %v", hash, err)
+	}
+}
+
+// removePublicBlobObject 引用归零后的物理回收：远程对象失败需上抛（与历史行为一致），
+// 本地文件失败只记日志（下次同内容上传会自愈覆盖）。
+func (s *UploadService) removePublicBlobObject(b model.Blob, localURL string) error {
+	if b.ObjectID != "" && s.ops != nil {
+		if e := s.ops.RemoveObject(b.ObjectID); e != nil {
+			return errors.New("记录已删除，远程文件清理未完成，请联系管理员")
+		}
+		return nil
+	}
+	if localURL == "" {
+		return nil
+	}
+	abs := filepath.Join(s.dir, filepath.FromSlash(strings.TrimPrefix(localURL, "/uploads/")))
+	if err := os.Remove(abs); err != nil && !os.IsNotExist(err) {
+		log.Printf("[upload] 删除 blob 文件失败 hash=%s path=%s: %v", b.Hash, abs, err)
+	}
+	return nil
+}
+
 func (s *UploadService) WithOperations(o *Operations) { s.ops = o }

backend/service/upload_webp_test.go

@@ -25,7 +25,7 @@ func newUploadTestService(t *testing.T) (*UploadService, string) {
 	if err != nil {
 		t.Fatalf("open sqlite: %v", err)
 	}
-	if err := db.AutoMigrate(&model.Attachment{}); err != nil {
+	if err := db.AutoMigrate(&model.Attachment{}, &model.Blob{}); err != nil {
 		t.Fatalf("migrate: %v", err)
 	}
 	dir := t.TempDir()