feat: 站点单页、时间线导入与行级 BBCode 短代码

首页右栏接入单页入口与公告置顶/全部页；Markdown 编辑器支持可视化时间线与 Git 导入；隐藏块改为 [hide]/[timeline] 命名闭合，并修复单页/公告 GORM 更新只改 updated_at 的问题。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/service/overview.go

@@ -51,6 +51,7 @@ type AnnouncementItem struct {
 	Title     string    `json:"title"`
 	Tag       string    `json:"tag"`
 	TagColor  string    `json:"tag_color"`
+	Pinned    bool      `json:"pinned"`
 	CreatedAt time.Time `json:"created_at"`
 }
 
@@ -65,13 +66,15 @@ type NewUserItem struct {
 
 // OverviewData 首页聚合数据
 type OverviewData struct {
-	Stats         OverviewStats      `json:"stats"`
-	Hot           []PostListItem     `json:"hot"`
-	ActiveUsers   []ActiveUser       `json:"active_users"`
-	Boards        []BoardCount       `json:"boards"`
-	Announcements []AnnouncementItem `json:"announcements"`
-	NewUsers      []NewUserItem      `json:"new_users"`
-	Checkin       *CheckinStatus     `json:"checkin,omitempty"`
+	Stats              OverviewStats      `json:"stats"`
+	Hot                []PostListItem     `json:"hot"`
+	ActiveUsers        []ActiveUser       `json:"active_users"`
+	Boards             []BoardCount       `json:"boards"`
+	Announcements      []AnnouncementItem `json:"announcements"`
+	AnnouncementsTotal int64              `json:"announcements_total"`
+	SidebarPages       []SidebarPageItem  `json:"sidebar_pages"`
+	NewUsers           []NewUserItem      `json:"new_users"`
+	Checkin            *CheckinStatus     `json:"checkin,omitempty"`
 }
 
 const (
@@ -98,6 +101,7 @@ func (s *OverviewService) Get() (*OverviewData, error) {
 		ActiveUsers:   []ActiveUser{},
 		Boards:        []BoardCount{},
 		Announcements: []AnnouncementItem{},
+		SidebarPages:  []SidebarPageItem{},
 		NewUsers:      []NewUserItem{},
 	}
 
@@ -230,10 +234,14 @@ LIMIT 5`
 		data.Boards = append(data.Boards, BoardCount{Board: b, PostCount: countMap[b.ID]})
 	}
 
-	// 站点公告（已发布，最新 5 条）
+	// 站点公告（已发布，置顶优先，最新 5 条）+ 总数
+	if err := s.db.Model(&model.Announcement{}).Where("published = ?", true).
+		Count(&data.AnnouncementsTotal).Error; err != nil {
+		return nil, err
+	}
 	var anns []model.Announcement
 	if err := s.db.Where("published = ?", true).
-		Order("created_at DESC, id DESC").Limit(5).Find(&anns).Error; err != nil {
+		Order("pinned DESC, created_at DESC, id DESC").Limit(5).Find(&anns).Error; err != nil {
 		return nil, err
 	}
 	for _, a := range anns {
@@ -242,10 +250,25 @@ LIMIT 5`
 			Title:     a.Title,
 			Tag:       a.Tag,
 			TagColor:  a.TagColor,
+			Pinned:    a.Pinned,
 			CreatedAt: a.CreatedAt,
 		})
 	}
 
+	// 侧栏单页入口（已发布且勾选侧栏）
+	var pages []model.SitePage
+	if err := s.db.Where("published = ? AND show_in_sidebar = ?", true, true).
+		Order("sort_order ASC, id ASC").
+		Select("id", "slug", "title", "excerpt").
+		Find(&pages).Error; err != nil {
+		return nil, err
+	}
+	for _, p := range pages {
+		data.SidebarPages = append(data.SidebarPages, SidebarPageItem{
+			ID: p.ID, Slug: p.Slug, Title: p.Title, Excerpt: p.Excerpt,
+		})
+	}
+
 	// 最新注册成员
 	var newUsers []model.User
 	if err := s.db.Select("id, username, nickname, avatar, created_at").