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/my_update_detail_page.dart

@@ -4,6 +4,7 @@ import 'package:flutter_screenutil/flutter_screenutil.dart';
 import 'package:go_router/go_router.dart';
 import 'package:new_learn/core/api/class/api.dart';
 import 'package:new_learn/core/api/class/model.dart';
+import 'package:new_learn/core/components/confirm_box.dart';
 import 'package:new_learn/core/components/user_circle_avatar.dart';
 import 'package:new_learn/core/providers/user_provider.dart';
 import 'package:new_learn/core/utils/img_url.dart';
@@ -41,30 +42,19 @@ class _MyUpdateDetailPageState extends ConsumerState<MyUpdateDetailPage> {
 
   /// 用详情接口增量更新评论相关字段（对标 Vue fetchDetail）
   ///
-  /// 关键：只有当 detail 确实带增量内容时才更新，且单个字段非空才覆盖。
-  /// 否则后端未返回评论/计数（空壳）时，会把列表带入的正确数据"清空"
-  /// —— 表现为初次闪现对的数据后瞬间空白。
+  /// 简化逻辑：接口成功返回就直接用详情数据覆盖评论相关字段，
+  /// 和 Vue 版一致（Vue 里 res.commons !== undefined 就直接覆盖）。
   Future<void> _fetchDetail() async {
     try {
       final res = await ClassApi.instance.getUserPostDetail(_post.id);
       if (!mounted) return;
-      // 空壳判定：detail 未携带任何有效增量 → 完全信任列表带入的数据，不更新
-      final hasDetail =
-          res.commons.isNotEmpty ||
-          res.userLikeAvatars.isNotEmpty ||
-          res.replyCount > 0 ||
-          res.likeCount > 0 ||
-          res.userLikeStatus;
-      if (!hasDetail) return;
       setState(() {
         _post = _post.copyWith(
-          commons: res.commons.isNotEmpty ? res.commons : _post.commons,
-          userLikeAvatars: res.userLikeAvatars.isNotEmpty
-              ? res.userLikeAvatars
-              : _post.userLikeAvatars,
+          commons: res.commons,
+          userLikeAvatars: res.userLikeAvatars,
           userLikeStatus: res.userLikeStatus,
-          replyCount: res.replyCount > 0 ? res.replyCount : _post.replyCount,
-          likeCount: res.likeCount > 0 ? res.likeCount : _post.likeCount,
+          replyCount: res.replyCount,
+          likeCount: res.likeCount,
         );
       });
     } catch (_) {
@@ -158,6 +148,7 @@ class _MyUpdateDetailPageState extends ConsumerState<MyUpdateDetailPage> {
                   onLike: _toggleLike,
                   onComment: (_) {},
                   hasCardBackground: false,
+                  showLikeCommentBar: false,
                 ),
                 _DetailComments(post: _post, onDelete: _deleteComment),
               ],
@@ -199,22 +190,10 @@ class _DetailCommentsState extends ConsumerState<_DetailComments> {
       _active = null;
       _pending = index;
     });
-    final ok = await showDialog<bool>(
-      context: context,
-      builder: (ctx) => AlertDialog(
-        title: const Text('是否删除评论'),
-        content: const Text('删除评论后将不可恢复，请慎重选择！'),
-        actions: [
-          TextButton(
-            onPressed: () => Navigator.pop(ctx, false),
-            child: const Text('取消'),
-          ),
-          TextButton(
-            onPressed: () => Navigator.pop(ctx, true),
-            child: const Text('确定'),
-          ),
-        ],
-      ),
+    final ok = await showConfirmBox(
+      context,
+      title: '是否删除评论',
+      content: '删除评论后将不可恢复，请慎重选择！',
     );
     if (!mounted) return;
     setState(() => _pending = null);
@@ -287,7 +266,12 @@ class _DetailCommentsState extends ConsumerState<_DetailComments> {
       );
     } else {
       for (int i = 0; i < _post.commons.length; i++) {
-        items.add(_commentItem(_post.commons[i], i, myId));
+        items.add(
+          Padding(
+            padding: EdgeInsets.symmetric(horizontal: 16.w),
+            child: _commentItem(_post.commons[i], i, myId),
+          ),
+        );
       }
     }
     items.add(SizedBox(height: 16.h));

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,
+                ),
             ],
           ),
         ),