feat(my): add 我的考试 page and related modules

1. 新增我的考试页面，包含学科筛选Tab和分页考试列表
2. 新增学科图标工具类，替换我的报告页重复的学科图标逻辑
3. 在我的页面菜单中添加我的考试入口
4. 新增exam模块的API接口和数据模型
5. 优化我的报告页面卡片样式，统一与考试卡片的布局

lib/core/api/exam/api.dart

@@ -0,0 +1,51 @@
+import 'package:new_learn/core/api/exam/model.dart';
+import 'package:new_learn/core/network/dio_client.dart';
+
+/// ============================================================
+/// 【exam 模块接口】我的考试 —— 对标 Vue3 端 api/exam/index.ts
+///
+///   getSubjects —— 获取考试学科筛选 Tab 列表
+///   search      —— 我的考试分页列表
+///
+/// 注意：考试报告详情（getReport）等考试做题相关接口，
+/// 后续扩展时再按模块拆分补进来。
+/// ============================================================
+class ExamApi {
+  ExamApi._();
+
+  static final ExamApi instance = ExamApi._();
+
+  /// 考试学科筛选 Tab 列表
+  /// GET /api/v1/Evaluation/GetSubjects
+  Future<List<ExamSubjectTab>> getSubjects() async {
+    final data = await DioClient.instance
+        .get('/api/v1/Evaluation/GetSubjects');
+    final list = data is List
+        ? data.whereType<Map<String, dynamic>>().toList()
+        : (data is Map<String, dynamic>
+                ? (data['data'] as List<dynamic>? ?? const [])
+                : const [])
+            .whereType<Map<String, dynamic>>()
+            .toList();
+    return list.map(ExamSubjectTab.fromJson).toList();
+  }
+
+  /// 我的考试分页列表
+  /// GET /api/v1/Evaluation/Search
+  /// 参数：baseSubjectId（可 null=全部）/ pageIndex / pageSize
+  Future<ExamResponse> search({
+    int? baseSubjectId,
+    required int pageIndex,
+    int pageSize = 10,
+  }) async {
+    final data = await DioClient.instance.get(
+      '/api/v1/Evaluation/Search',
+      query: {
+        if (baseSubjectId != null) 'baseSubjectId': baseSubjectId,
+        'pageIndex': pageIndex,
+        'pageSize': pageSize,
+      },
+    );
+    return ExamResponse.fromJson(data as Map<String, dynamic>);
+  }
+}

lib/core/api/exam/model.dart

@@ -0,0 +1,109 @@
+/// ============================================================
+/// 【exam 模块模型】我的考试 —— 对标 Vue3 端 api/exam/type.ts
+///
+///   ExamDto          —— 单条考试记录
+///   ExamSubjectTab   —— 考试科目筛选 Tab
+///   ExamResponse     —— 考试列表分页响应
+///
+/// 序列化：手动 fromJson，与项目其他模块风格一致，不依赖 build_runner。
+///
+/// ⚠ 注意：后端返回的 id 字段类型不统一（数字 or 字符串），
+/// 所有数值字段统一用 _asInt() 做兼容解析，避免类型转换异常。
+/// ============================================================
+library;
+
+int? _optInt(dynamic v) {
+  if (v == null) return null;
+  if (v is int) return v;
+  if (v is double) return v.toInt();
+  final s = v.toString();
+  final n = int.tryParse(s);
+  if (n != null) return n;
+  return double.tryParse(s)?.toInt();
+}
+
+int _asInt(dynamic v, [int fallback = 0]) => _optInt(v) ?? fallback;
+
+/// 单条考试记录
+class ExamDto {
+  const ExamDto({
+    this.id = 0,
+    this.taskId = 0,
+    this.taskName = '',
+    this.baseSubjectId = 0,
+    this.baseSubjectName = '',
+    this.startTime = '',
+    this.endTime = '',
+    this.totalScore = 0,
+    this.userScore = 0,
+  });
+
+  final int id;
+  final int taskId;
+  final String taskName;
+  final int baseSubjectId;
+  final String baseSubjectName;
+  final String startTime;
+  final String endTime;
+  final int totalScore;
+  final int userScore;
+
+  factory ExamDto.fromJson(Map<String, dynamic> json) {
+    return ExamDto(
+      id: _asInt(json['id']),
+      taskId: _asInt(json['taskId']),
+      taskName: (json['taskName'] as String?) ?? '',
+      baseSubjectId: _asInt(json['baseSubjectId']),
+      baseSubjectName: (json['baseSubjectName'] as String?) ?? '',
+      startTime: (json['startTime'] as String?) ?? '',
+      endTime: (json['endTime'] as String?) ?? '',
+      totalScore: _asInt(json['totalScore']),
+      userScore: _asInt(json['userScore']),
+    );
+  }
+}
+
+/// 考试科目筛选 Tab
+class ExamSubjectTab {
+  const ExamSubjectTab({this.id, this.name = ''});
+
+  /// 为 null 表示"全部"
+  final int? id;
+  final String name;
+
+  factory ExamSubjectTab.fromJson(Map<String, dynamic> json) {
+    return ExamSubjectTab(
+      id: _optInt(json['id']),
+      name: (json['name'] as String?) ?? '',
+    );
+  }
+}
+
+/// 考试列表分页响应
+class ExamResponse {
+  const ExamResponse({
+    this.data = const [],
+    this.total = 0,
+    this.pageIndex = 1,
+    this.pageSize = 10,
+  });
+
+  final List<ExamDto> data;
+  final int total;
+  final int pageIndex;
+  final int pageSize;
+
+  factory ExamResponse.fromJson(Map<String, dynamic> json) {
+    final payload = (json['data'] as Map<String, dynamic>?) ?? json;
+    final list = (payload['data'] as List<dynamic>? ?? const [])
+        .whereType<Map<String, dynamic>>()
+        .map(ExamDto.fromJson)
+        .toList();
+    return ExamResponse(
+      data: list,
+      total: (payload['total'] as num?)?.toInt() ?? list.length,
+      pageIndex: (payload['pageIndex'] as num?)?.toInt() ?? 1,
+      pageSize: (payload['pageSize'] as num?)?.toInt() ?? 10,
+    );
+  }
+}