Replace websocket flow with SSE support in backend.

Update handlers, services, router, and data conversion logic to support server-sent events and related message pipeline changes.

Made-with: Cursor

internal/model/post.go

@@ -58,7 +58,7 @@ type Post struct {
 
 	// 时间戳
 	CreatedAt time.Time `json:"created_at" gorm:"autoCreateTime;index:idx_posts_status_created,priority:2,sort:desc;index:idx_posts_user_status_created,priority:3,sort:desc;index:idx_posts_hot_score_created,priority:2,sort:desc"`
-	UpdatedAt time.Time `json:"updated_at" gorm:"autoUpdateTime"`
+	UpdatedAt time.Time `json:"updated_at" gorm:"autoUpdateTime:false"`
 }
 
 // BeforeCreate 创建前生成UUID