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 ----------

lib/core/router/main_tab_page.dart

@@ -37,10 +37,11 @@ import 'package:new_learn/core/version/app_version_service.dart';
 ///      底部导航不消失、子页面盖在内容区上——这是 ShellRoute 的价值。
 /// ============================================================
 class MainTabPage extends StatefulWidget {
-  const MainTabPage({super.key, required this.child});
+  const MainTabPage({super.key, required this.navigationShell});
 
-  /// 当前 tab 页面（由 go_router ShellRoute 提供）
-  final Widget child;
+  /// go_router 的导航壳（StatefulShellRoute.indexedStack 提供）：
+  /// 内部用 IndexedStack 保活各 tab 页面，来回切 tab 不丢页面状态。
+  final StatefulNavigationShell navigationShell;
 
   @override
   State<MainTabPage> createState() => _MainTabPageState();
@@ -100,37 +101,19 @@ class _MainTabPageState extends State<MainTabPage> {
     'assets/img/tabbar/default/myChoose.png',
   ];
 
-  /// 当前路由 path → tab 序号（默认第 1 个"任务"）
-  int _indexOf(String path) {
-    return switch (path) {
-      '/recite' => 1,
-      '/class' => 2,
-      '/my' => 3,
-      _ => 0,
-    };
-  }
-
-  /// tab 序号 → 路由 path（点击底部导航时跳转）
-  String _pathOf(int index) {
-    return switch (index) {
-      1 => '/recite',
-      2 => '/class',
-      3 => '/my',
-      _ => '/',
-    };
-  }
-
   @override
   Widget build(BuildContext context) {
-    // 从 go_router 拿当前路由，反推底部高亮 tab
-    final path = GoRouterState.of(context).uri.path;
-    final currentIndex = _indexOf(path);
+    final navigationShell = widget.navigationShell;
+    final currentIndex = navigationShell.currentIndex;
 
     return Scaffold(
-      body: widget.child,
+      body:
+          navigationShell, // StatefulNavigationShell 内部用 IndexedStack 保活各 tab 页
       bottomNavigationBar: BottomNavigationBar(
         currentIndex: currentIndex,
-        onTap: (i) => context.go(_pathOf(i)),
+        // 切 tab：进对应 branch；点当前 tab 则回到其栈顶
+        onTap: (i) =>
+            navigationShell.goBranch(i, initialLocation: i == currentIndex),
         type: BottomNavigationBarType.fixed,
         backgroundColor: Colors.white,
         selectedItemColor: const Color(0xFF3B82F6),