xhs_get_comments 增加 sort + max_count 控制，评论随详情一起返回

- Comment 新增 subCommentCount，新增 CommentsResult 接口
- GetFeedCommentsSchema 替换 load_all 为 sort (default/newest/most_liked) + max_count (1-100)
- getFeedDetail 不再清空评论，从 Vue store 异步提取首屏评论（轮询 firstRequestFinish）
- getFeedComments 重写：支持排序切换、按 maxCount 加载、返回 hasMore/totalCount
- 前端详情加载后直接显示评论，无需单独请求；底部显示"加载更多评论"按钮
- CommentTree 显示"还有 X 条回复"提示
- 修复 formatTime 对空字符串和无效日期的处理

web/src/api/endpoints.ts

@@ -4,6 +4,7 @@ import type {
   QRCodeResult,
   Feed,
   FeedDetail,
+  CommentsResult,
   UserProfile,
   SearchFilters,
   HealthResponse,
@@ -40,10 +41,21 @@ export const searchFeeds = (keyword: string, filters?: SearchFilters) =>
     body: JSON.stringify({ keyword, filters }),
   });
 
-export const getFeedDetail = (feedId: string, xsecToken: string, loadAllComments = false) =>
+export const getFeedDetail = (feedId: string, xsecToken: string) =>
   apiFetch<ApiResponse<FeedDetail>>('/api/xhs/feeds/detail', {
     method: 'POST',
-    body: JSON.stringify({ feed_id: feedId, xsec_token: xsecToken, load_all_comments: loadAllComments }),
+    body: JSON.stringify({ feed_id: feedId, xsec_token: xsecToken }),
+  });
+
+export const getFeedComments = (
+  feedId: string,
+  xsecToken: string,
+  sort: 'default' | 'newest' | 'most_liked' = 'default',
+  maxCount = 20,
+) =>
+  apiFetch<ApiResponse<CommentsResult>>('/api/xhs/feeds/comments', {
+    method: 'POST',
+    body: JSON.stringify({ feed_id: feedId, xsec_token: xsecToken, sort, max_count: maxCount }),
   });
 
 // User