feat: app 骨架 + 网络层 + 认证（登录/注册）

- flutter create 初始化 + 依赖（riverpod 3/dio/go_router/three_dart 0.0.16）
- ApiClient：JWT 拦截器 + 统一响应解包 + 401 登出回调 + multipart 上传
- TokenStorage（shared_preferences）+ AuthNotifier 登录/登出
- 登录页（含注册对话框）+ 4 Tab 主框架
- 6 个单元测试通过（网络层 4 + 认证 2）

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/core/network/api_client.dart

@@ -0,0 +1,77 @@
+import 'package:dio/dio.dart';
+
+import '../config/app_config.dart';
+import '../storage/token_storage.dart';
+import 'api_exception.dart';
+
+/// 统一网络客户端：JWT 拦截器 + 统一响应解包（code != 0 抛 ApiException）
+class ApiClient {
+  final TokenStorage _tokenStorage;
+  late final Dio _dio;
+
+  /// 401 时回调（登出）
+  void Function()? onUnauthorized;
+
+  // ignore: prefer_initializing_formals
+  ApiClient({required TokenStorage tokenStorage, Dio? dio})
+      : _tokenStorage = tokenStorage {
+    _dio = dio ??
+        Dio(BaseOptions(
+          baseUrl: AppConfig.baseUrl,
+          connectTimeout: const Duration(seconds: 10),
+          receiveTimeout: const Duration(seconds: 60),
+        ));
+    _dio.interceptors.add(InterceptorsWrapper(
+      onRequest: (options, handler) {
+        final token = _tokenStorage.token;
+        if (token != null && token.isNotEmpty) {
+          options.headers['Authorization'] = 'Bearer $token';
+        }
+        handler.next(options);
+      },
+      onError: (e, handler) {
+        if (e.response?.statusCode == 401) onUnauthorized?.call();
+        handler.next(e);
+      },
+    ));
+  }
+
+  Future<T> post<T>(String path, Map<String, dynamic> body,
+      {T Function(dynamic data)? parse}) async {
+    final res = await _dio.post(path, data: body);
+    return _unwrap(res, parse);
+  }
+
+  Future<T> get<T>(String path,
+      {Map<String, dynamic>? query, T Function(dynamic data)? parse}) async {
+    final res = await _dio.get(path, queryParameters: query);
+    return _unwrap(res, parse);
+  }
+
+  /// multipart 上传：fields 为文本字段，fileField 为文件字段名
+  Future<T> upload<T>(String path, Map<String, dynamic> fields,
+      String fileField, String filePath,
+      {T Function(dynamic data)? parse}) async {
+    final form = FormData.fromMap({
+      ...fields,
+      fileField: await MultipartFile.fromFile(filePath),
+    });
+    final res = await _dio.post(path, data: form);
+    return _unwrap(res, parse);
+  }
+
+  T _unwrap<T>(Response res, T Function(dynamic data)? parse) {
+    final data = res.data;
+    if (data is! Map<String, dynamic>) {
+      throw ApiException(-1, '响应格式错误');
+    }
+    final code = data['code'] as int? ?? -1;
+    final message = data['message'] as String? ?? '';
+    if (code != 0) {
+      throw ApiException(code, message);
+    }
+    final payload = data['data'];
+    if (parse != null) return parse(payload);
+    return payload as T;
+  }
+}

lib/core/network/api_exception.dart

@@ -0,0 +1,10 @@
+/// 业务异常（后端统一响应 code != 0）
+class ApiException implements Exception {
+  final int code;
+  final String message;
+
+  ApiException(this.code, this.message);
+
+  @override
+  String toString() => message;
+}