feat: 代码片段功能与 Markdown 内嵌片段渲染、文档截图等

backend/model/db.go

@@ -64,6 +64,7 @@ func InitDB(dsn string) error {
 		&Badge{}, &UserBadge{},
 		&PostPollVote{}, &PostLotteryEntry{}, &Ad{}, &SidebarWidget{}, &FriendLink{},
 		&ImportRecord{}, &LibraryDoc{}, &LibraryFile{}, &LibrarySection{},
+		&CodeSnippet{}, &SnippetVersion{}, &SnippetComment{}, &SnippetCommentEditHistory{},
 	); err != nil {
 		return fmt.Errorf("自动迁移失败: %w", err)
 	}

backend/model/models.go

@@ -576,6 +576,75 @@ type LibrarySection struct {
 	DeletedAt gorm.DeletedAt `gorm:"index" json:"-"`
 }
 
+// CodeSnippet 代码片段：用户所有，公开进广场，私有仅自己可见
+type CodeSnippet struct {
+	ID           uint           `gorm:"primaryKey" json:"id"`
+	Title        string         `gorm:"size:120;not null" json:"title"`
+	Description  string         `gorm:"type:text" json:"description"`
+	Language     string         `gorm:"size:32;not null;index" json:"language"`
+	Code         string         `gorm:"type:text;not null" json:"code"`
+	Visibility   string         `gorm:"size:16;not null;default:private;index" json:"visibility"` // public/private
+	UserID       uint           `gorm:"index;not null" json:"user_id"`
+	ForkedFromID *uint          `gorm:"index" json:"forked_from_id"`
+	CopyCount    int            `gorm:"not null;default:0" json:"copy_count"`
+	ViewCount    int            `gorm:"not null;default:0" json:"view_count"`
+	CommentCount int            `gorm:"not null;default:0" json:"comment_count"`
+	ForkCount    int            `gorm:"not null;default:0" json:"fork_count"`
+	CreatedAt    time.Time      `json:"created_at"`
+	UpdatedAt    time.Time      `json:"updated_at"`
+	DeletedAt    gorm.DeletedAt `gorm:"index" json:"-"`
+}
+
+// SnippetVersion 编辑前旧值快照（同 PostEditHistory 思路）
+type SnippetVersion struct {
+	ID             uint      `gorm:"primaryKey" json:"id"`
+	SnippetID      uint      `gorm:"index;not null" json:"snippet_id"`
+	EditorID       uint      `gorm:"index;not null" json:"editor_id"`
+	OldTitle       string    `gorm:"size:120;not null;default:''" json:"old_title"`
+	OldLanguage    string    `gorm:"size:32;not null;default:''" json:"old_language"`
+	OldDescription string    `gorm:"type:text" json:"old_description"`
+	OldCode        string    `gorm:"type:text;not null" json:"old_code"`
+	CreatedAt      time.Time `gorm:"index" json:"created_at"`
+}
+
+// SnippetComment 片段评论（楼层树：ParentID 空=主评，非空=回复；RootID=所属主楼）
+type SnippetComment struct {
+	ID         uint           `gorm:"primaryKey" json:"id"`
+	SnippetID  uint           `gorm:"index;not null" json:"snippet_id"`
+	UserID     uint           `gorm:"index;not null" json:"user_id,omitempty"`
+	ParentID   *uint          `gorm:"index" json:"parent_id"`
+	RootID     *uint          `gorm:"index" json:"root_id"`
+	Depth      int            `gorm:"not null;default:0" json:"depth"`
+	Content    string         `gorm:"type:text;not null" json:"content"`
+	DeleteType string         `gorm:"size:32;default:''" json:"delete_type,omitempty"`
+	DeletedBy  uint           `gorm:"not null;default:0" json:"deleted_by,omitempty"`
+	CreatedAt  time.Time      `json:"created_at"`
+	UpdatedAt  time.Time      `json:"updated_at"`
+	DeletedAt  gorm.DeletedAt `gorm:"index" json:"-"`
+}
+
+// SnippetCommentEditHistory 片段评论修订快照（每次编辑前的旧正文；登录用户可见）
+type SnippetCommentEditHistory struct {
+	ID         uint      `gorm:"primaryKey" json:"id"`
+	CommentID  uint      `gorm:"index;not null" json:"comment_id"`
+	EditorID   uint      `gorm:"index;not null" json:"editor_id"`
+	OldContent string    `gorm:"type:text;not null" json:"old_content"`
+	CreatedAt  time.Time `gorm:"index" json:"created_at"`
+}
+
+const (
+	SnippetVisibilityPublic  = "public"
+	SnippetVisibilityPrivate = "private"
+)
+
+// NormalizeSnippetVisibility 归一化可见性：空或未知值一律回落 private
+func NormalizeSnippetVisibility(v string) string {
+	if v == SnippetVisibilityPublic {
+		return SnippetVisibilityPublic
+	}
+	return SnippetVisibilityPrivate
+}
+
 // SiteSetting 站点级键值设置（如历史在线峰值 peak_online）
 type SiteSetting struct {
 	Key       string    `gorm:"primaryKey;size:64" json:"key"`