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/components/business/PostCard.tsx

@@ -135,12 +135,24 @@ const PostCard: React.FC<PostCardProps> = ({
     return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}`;
   };
 
-  const isPostEdited = (createdAt?: string, updatedAt?: string): boolean => {
-    if (!createdAt || !updatedAt) return false;
-    const created = new Date(createdAt).getTime();
-    const updated = new Date(updatedAt).getTime();
-    if (Number.isNaN(created) || Number.isNaN(updated)) return false;
-    return updated - created > 1000;
+  /** 返回应展示的「最后编辑」时间字符串；优先 content_edited_at（与点赞/评论等统计更新解耦） */
+  const getPostEditedDisplayAt = (
+    createdAt?: string | null,
+    contentEditedAt?: string | null,
+    updatedAt?: string | null,
+  ): string | null => {
+    if (contentEditedAt) {
+      const c = new Date(createdAt || '').getTime();
+      const e = new Date(contentEditedAt).getTime();
+      if (!Number.isNaN(c) && !Number.isNaN(e) && e - c > 1000) return contentEditedAt;
+      return null;
+    }
+    if (createdAt && updatedAt) {
+      const c = new Date(createdAt).getTime();
+      const u = new Date(updatedAt).getTime();
+      if (!Number.isNaN(c) && !Number.isNaN(u) && u - c > 1000) return updatedAt;
+    }
+    return null;
   };
 
   const getTruncatedContent = (content: string | undefined | null, maxLength: number = 100): string => {
@@ -560,11 +572,18 @@ const PostCard: React.FC<PostCardProps> = ({
             <Text variant="caption" color={colors.text.hint} style={styles.timeText}>
               发布 {formatDateTime(post.created_at)}
             </Text>
-            {isPostEdited(post.created_at, post.updated_at) && (
+            {(() => {
+              const editedAt = getPostEditedDisplayAt(
+                post.created_at,
+                post.content_edited_at,
+                post.updated_at,
+              );
+              return editedAt ? (
               <Text variant="caption" color={colors.text.hint} style={styles.timeText}>
-                {' · 修改 '}{formatDateTime(post.updated_at)}
+                {' · 修改 '}{formatDateTime(editedAt)}
               </Text>
-            )}
+              ) : null;
+            })()}
           </View>
         </View>
         {post.is_pinned && (