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/core/router/app_router.dart

@@ -6,7 +6,11 @@ import 'package:new_learn/features/auth/legal_document_page.dart';
 import 'package:new_learn/features/auth/legal_documents.dart';
 import 'package:new_learn/features/auth/login_page.dart';
 import 'package:new_learn/features/auth/privacy_consent_page.dart';
+import 'package:new_learn/features/class/all_student_view.dart';
 import 'package:new_learn/features/class/class_page.dart';
+import 'package:new_learn/features/class/my_interact_page.dart';
+import 'package:new_learn/features/class/my_update_detail_page.dart';
+import 'package:new_learn/core/api/class/model.dart';
 import 'package:new_learn/features/my/my_page.dart';
 import 'package:new_learn/features/my/my_point/my_point_page.dart';
 import 'package:new_learn/features/recite/recite_page.dart';
@@ -76,14 +80,47 @@ final GoRouter appRouter = GoRouter(
     privacyAcceptedNotifier,
   ]), // 响应式登录守卫：监听登录态变化信号，变化时自动重算 redirect
   routes: [
-    // ---------- 4 tab 主框架（ShellRoute：子页面共享这个壳） ----------
-    ShellRoute(
-      builder: (context, state, child) => MainTabPage(child: child),
-      routes: [
-        GoRoute(path: '/', builder: (_, _) => const TaskPage()),
-        GoRoute(path: '/recite', builder: (_, _) => const RecitePage()),
-        GoRoute(path: '/class', builder: (_, _) => const ClassPage()),
-        GoRoute(path: '/my', builder: (_, _) => const MyPage()),
+    // ---------- 4 tab 主框架（StatefulShellRoute：切 tab 用 IndexedStack 保活页面状态） ----------
+    StatefulShellRoute.indexedStack(
+      builder: (context, state, navigationShell) =>
+          MainTabPage(navigationShell: navigationShell),
+      branches: [
+        // 任务
+        StatefulShellBranch(
+          routes: [GoRoute(path: '/', builder: (_, _) => const TaskPage())],
+        ),
+        // 背诵
+        StatefulShellBranch(
+          routes: [
+            GoRoute(path: '/recite', builder: (_, _) => const RecitePage()),
+          ],
+        ),
+        // 班级（含班级模块子页：全部同学 / 我的互动 / 动态详情）
+        StatefulShellBranch(
+          routes: [
+            GoRoute(path: '/class', builder: (_, _) => const ClassPage()),
+            GoRoute(
+              path: '/class/all-student',
+              builder: (_, _) => const AllStudentPage(),
+            ),
+            GoRoute(
+              path: '/class/my-interact',
+              builder: (_, _) => const MyInteractPage(),
+            ),
+            GoRoute(
+              path: '/class/my-update-detail',
+              builder: (_, state) =>
+                  MyUpdateDetailPage(initialPost: state.extra as UserPostDto),
+            ),
+          ],
+        ),
+        // 我的（含我的积分页）
+        StatefulShellBranch(
+          routes: [
+            GoRoute(path: '/my', builder: (_, _) => const MyPage()),
+            GoRoute(path: '/myPoint', builder: (_, _) => const MyPointPage()),
+          ],
+        ),
       ],
     ),
     // ---------- 首次启动隐私协议页 ----------
@@ -107,8 +144,6 @@ final GoRouter appRouter = GoRouter(
     ),
     // ---------- 登录页 ----------
     GoRoute(path: '/login', builder: (_, _) => const LoginPage()),
-    // ---------- 业务子页（从 tab 页 push 进来，不占 tab） ----------
-    GoRoute(path: '/myPoint', builder: (_, _) => const MyPointPage()),
     // app_router.dart 的 routes 里加，不用管跳转逻辑
     // GoRoute(path: '/task/:id', builder: (_, _) => const TaskDetailPage()),
     // ---------- 以后新业务页在这里加，一行一个 ----------