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/api/class/model.dart

@@ -21,6 +21,7 @@ class UserPostCommonDto {
     this.content = '',
     this.createTime = '',
     this.id = 0,
+    this.avatar = '',
   });
 
   final int userId;
@@ -28,6 +29,7 @@ class UserPostCommonDto {
   final String content;
   final String createTime;
   final int id;
+  final String avatar;
 
   factory UserPostCommonDto.fromJson(Map<String, dynamic> json) =>
       UserPostCommonDto(
@@ -36,6 +38,8 @@ class UserPostCommonDto {
         content: json['content'] as String? ?? '',
         createTime: json['createTime'] as String? ?? '',
         id: _toInt(json['id']),
+        // 详情接口的留言项带评论者头像
+        avatar: json['avatar'] as String? ?? '',
       );
 }
 
@@ -248,13 +252,16 @@ class UserRankPagedList {
     final ranksList = payload['userRanks'] is List
         ? payload['userRanks'] as List<dynamic>
         : (payload['data'] is List
-        ? payload['data'] as List<dynamic>
-        : const []);
+              ? payload['data'] as List<dynamic>
+              : const []);
     return UserRankPagedList(
       myRank: payload['myRank'] is Map<String, dynamic>
           ? UserRank.fromJson(payload['myRank'] as Map<String, dynamic>)
           : null,
-      userRanks: ranksList.whereType<Map<String, dynamic>>().map(UserRank.fromJson).toList(),
+      userRanks: ranksList
+          .whereType<Map<String, dynamic>>()
+          .map(UserRank.fromJson)
+          .toList(),
       total: _toInt(payload['total']),
       pageIndex: _toInt(payload['pageIndex']),
       pageSize: _toInt(payload['pageSize']),
@@ -304,4 +311,4 @@ int? _toIntOrNull(dynamic v) {
   if (v is num) return v.toInt();
   if (v is String) return int.tryParse(v);
   return null;
-}
+}