refactor(PostCard, ImageGrid, SmartImage): enhance post editing display and image handling

- Introduced a new method to determine the last edited time for posts, prioritizing content_edited_at for better accuracy in display.
- Updated PostCard and PostDetailScreen components to utilize the new editing display logic.
- Enhanced ImageGrid and SmartImage components to support additional preview URLs and improve image loading behavior, including lazy loading optimizations for web.
- Modified Post and PostDTO interfaces to include contentEditedAt for better tracking of post edits.

src/core/entities/Post.ts

@@ -81,7 +81,9 @@ export interface Post {
   createdAt: string;
   /** 更新时间 */
   updatedAt: string;
-  
+  /** 用户编辑内容的时间（与统计类更新解耦） */
+  contentEditedAt?: string;
+
   // ==================== 向后兼容字段 (snake_case) ====================
   // 这些字段用于与旧代码兼容，新代码应使用 camelCase 版本
   
@@ -107,6 +109,8 @@ export interface Post {
   created_at?: string;
   /** @deprecated 请使用 updatedAt */
   updated_at?: string;
+  /** @deprecated 请使用 contentEditedAt */
+  content_edited_at?: string;
   /** @deprecated 请使用 communityId */
   community_id?: string;
   /** @deprecated 请使用 status */