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/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
 }