refactor(class): 优化接口请求与页面细节

1. 统一处理后端统一包结构，自动解析data字段
2. 新增点赞评论栏显示控制参数，详情页隐藏该栏
3. 简化详情页数据更新逻辑，对齐Vue版本实现
4. 重构确认弹窗组件，优化样式与弹窗尺寸
5. 为评论项添加水平边距，优化列表排版

lib/features/class/widgets/class_update_widgets.dart

@@ -28,6 +28,7 @@ class PostCard extends StatelessWidget {
     required this.onComment,
     this.showCommentComposer = true,
     this.hasCardBackground = true,
+    this.showLikeCommentBar = true,
   });
 
   final UserPostDto post;
@@ -40,6 +41,9 @@ class PostCard extends StatelessWidget {
   /// 是否显示白色卡片背景（列表页 true；详情页与留言区共用一张大卡片 → false）
   final bool hasCardBackground;
 
+  /// 是否显示点赞/评论标记栏（列表页 true；详情页不需要 → false）
+  final bool showLikeCommentBar;
+
   String get _avatar {
     final url = ImgUrl.build(post.avatar);
     return url.isEmpty
@@ -96,12 +100,13 @@ class PostCard extends StatelessWidget {
                 AlbumGrid(urls: post.urls.map(ImgUrl.build).toList()),
               ],
               SizedBox(height: 10.h),
-              LikeCommentBar(
-                post: post,
-                onLike: onLike,
-                onComment: onComment,
-                showComposer: showCommentComposer,
-              ),
+              if (showLikeCommentBar)
+                LikeCommentBar(
+                  post: post,
+                  onLike: onLike,
+                  onComment: onComment,
+                  showComposer: showCommentComposer,
+                ),
             ],
           ),
         ),