feat: 完成班级模块全量功能迭代

本次提交完成了班级模块的多项核心功能开发与优化：
1. 新增DELETE请求封装，支持业务删除接口且不自动重试
2. 完善UserPostCommonDto模型，新增头像字段适配详情接口
3. 重构路由架构，使用StatefulShellRoute实现Tab页面保活
4. 新增我的互动页面，包含我的动态/点赞/留言三个子页
5. 新增全部同学页面，展示班级全员信息与在线状态
6. 新增动态详情页面，支持查看完整评论与点赞头像
7. 抽离通用PostListBody组件，复用列表分页与交互逻辑
8. 优化班级列表页加载逻辑与图片预览交互
9. 新增评论删除、多图预览等细节交互功能

lib/features/class/class_update_view.dart

@@ -2,6 +2,8 @@ import 'package:cached_network_image/cached_network_image.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_screenutil/flutter_screenutil.dart';
+import 'package:go_router/go_router.dart';
+import 'package:new_learn/core/components/image_preview_viewer.dart';
 import 'package:new_learn/core/components/user_circle_avatar.dart';
 import 'package:new_learn/core/models/user_model.dart';
 import 'package:new_learn/core/providers/user_provider.dart';
@@ -121,7 +123,10 @@ class _ClassUpdateViewState extends ConsumerState<ClassUpdateView> {
           ..addAll(res.data);
         _pageIndex = 1;
         _prevPageId = res.data.isNotEmpty ? res.data.last.id : 0;
-        _hasMore = res.data.length >= _pageSize;
+        // 优先用总条数判断是否还有更多；total 不可用时退回"本页满页才继续"
+        _hasMore = res.total > 0
+            ? res.data.length < res.total
+            : res.data.length >= _pageSize;
         _loading = false;
       });
     } catch (_) {
@@ -147,7 +152,10 @@ class _ClassUpdateViewState extends ConsumerState<ClassUpdateView> {
         _posts.addAll(res.data);
         _pageIndex += 1;
         if (res.data.isNotEmpty) _prevPageId = res.data.last.id;
-        _hasMore = res.data.length >= _pageSize;
+        // 累计长度 vs 总条数，即使每页都返回满页也能在到底后正确收尾
+        _hasMore = res.total > 0
+            ? _posts.length < res.total
+            : res.data.length >= _pageSize;
         _loadingMore = false;
       });
     } catch (_) {
@@ -258,24 +266,43 @@ class _ClassUpdateViewState extends ConsumerState<ClassUpdateView> {
         controller: _scrollController,
         physics: const AlwaysScrollableScrollPhysics(),
         padding: EdgeInsets.symmetric(horizontal: 14.w),
-        itemCount: _posts.length + (_hasMore ? 1 : 0),
+        itemCount: _posts.length + 1,
         itemBuilder: (context, index) {
           if (index >= _posts.length) {
+            // 底部占位：加载中显示菊花，没有更多则显示提示文案
+            if (_hasMore) {
+              return Padding(
+                padding: EdgeInsets.symmetric(vertical: 16.h),
+                child: const Center(
+                  child: SizedBox(
+                    width: 22,
+                    height: 22,
+                    child: CircularProgressIndicator(strokeWidth: 2.5),
+                  ),
+                ),
+              );
+            }
             return Padding(
-              padding: EdgeInsets.symmetric(vertical: 16.h),
-              child: const Center(
-                child: SizedBox(
-                  width: 22,
-                  height: 22,
-                  child: CircularProgressIndicator(strokeWidth: 2.5),
+              padding: EdgeInsets.symmetric(vertical: 20.h),
+              child: Center(
+                child: Text(
+                  '没有更多了',
+                  style: TextStyle(
+                    fontSize: 12.sp,
+                    color: const Color(0xFFB4C2E0),
+                  ),
                 ),
               ),
             );
           }
-          return PostCard(
-            post: _posts[index],
-            onLike: () => _toggleLike(index),
-            onComment: (content) => _submitComment(index, content),
+          final post = _posts[index];
+          return GestureDetector(
+            onTap: () => context.push('/class/my-update-detail', extra: post),
+            child: PostCard(
+              post: post,
+              onLike: () => _toggleLike(index),
+              onComment: (content) => _submitComment(index, content),
+            ),
           );
         },
       ),
@@ -357,39 +384,49 @@ class _ClassUpdateViewState extends ConsumerState<ClassUpdateView> {
           for (int i = 0; i < urls.length; i++)
             Positioned(
               left: i * overlap,
-              child: UserCircleAvatar(url: urls[i], radius: size / 2),
+              child: GestureDetector(
+                // 点头像 → 大图预览单张
+                onTap: () => ImagePreviewViewer.showSingle(
+                  context,
+                  imageProvider: CachedNetworkImageProvider(urls[i]),
+                ),
+                child: UserCircleAvatar(url: urls[i], radius: size / 2),
+              ),
             ),
         ],
       ),
     );
   }
 
-  /// 右侧「全部」按钮
+  /// 右侧「全部」按钮 → 全部同学页
   Widget _buildAllButton() {
-    return Container(
-      width: 62.w,
-      height: 34.h,
-      alignment: Alignment.center,
-      decoration: BoxDecoration(
-        gradient: const LinearGradient(
-          begin: Alignment.topCenter,
-          end: Alignment.bottomCenter,
-          colors: [Color(0xFF3D7DF5), Color(0xFF3C84FF), Color(0xFF8AD1FD)],
+    return GestureDetector(
+      onTap: () => context.push('/class/all-student'),
+      child: Container(
+        width: 62.w,
+        height: 34.h,
+        alignment: Alignment.center,
+        decoration: BoxDecoration(
+          gradient: const LinearGradient(
+            begin: Alignment.topCenter,
+            end: Alignment.bottomCenter,
+            colors: [Color(0xFF3D7DF5), Color(0xFF3C84FF), Color(0xFF8AD1FD)],
+          ),
+          borderRadius: BorderRadius.only(
+            topRight: Radius.circular(15.r),
+            bottomLeft: Radius.circular(15.r),
+            bottomRight: Radius.circular(20.r),
+          ),
         ),
-        borderRadius: BorderRadius.only(
-          topRight: Radius.circular(15.r),
-          bottomLeft: Radius.circular(15.r),
-          bottomRight: Radius.circular(20.r),
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            Text('全部', style: TextStyle(fontSize: 14, color: Colors.white)),
+            SizedBox(width: 2.w),
+            Icon(Icons.chevron_right, size: 14, color: Colors.white),
+          ],
         ),
       ),
-      child: Row(
-        mainAxisSize: MainAxisSize.min,
-        children: [
-          Text('全部', style: TextStyle(fontSize: 14, color: Colors.white)),
-          SizedBox(width: 2.w),
-          Icon(Icons.chevron_right, size: 14, color: Colors.white),
-        ],
-      ),
     );
   }