chore: 全面规范化代码，遵循 CLAUDE.md 编码规范

- C# 文件命名改为 snake_case（28 个文件重命名）
- C# 类转换为主构造函数（8 个类）
- 空 catch 添加异常类型（2 处）
- 新建 GlobalUsings.cs（Health.Infrastructure、Health.WebApi）
- Flutter 移除 go_router，改用 Riverpod 路由栈
- Flutter 移除 flutter_secure_storage，改用 sqflite 持久化
- 修复 Flutter 构建路径（Flutter SDK 迁至 D 盘）
- 后端端口改为 0.0.0.0:5000，支持局域网访问

health_app/lib/providers/auth_provider.dart

@@ -1,7 +1,7 @@
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:dio/dio.dart';
 import '../core/api_client.dart';
-import '../core/secure_storage.dart';
+import '../core/local_database.dart';
 
 /// 用户简要信息
 class UserInfo {
@@ -25,10 +25,10 @@ class AuthState {
 /// 认证 Provider
 final authProvider = NotifierProvider<AuthNotifier, AuthState>(AuthNotifier.new);
 
-final secureStorageProvider = Provider<SecureStorage>((ref) => SecureStorage());
+final localDbProvider = Provider<LocalDatabase>((ref) => LocalDatabase.instance);
 
 final apiClientProvider = Provider<ApiClient>((ref) {
-  return ApiClient(storage: ref.watch(secureStorageProvider));
+  return ApiClient(db: ref.watch(localDbProvider));
 });
 
 class AuthNotifier extends Notifier<AuthState> {
@@ -39,8 +39,8 @@ class AuthNotifier extends Notifier<AuthState> {
   }
 
   Future<void> _checkAuth() async {
-    final storage = ref.read(secureStorageProvider);
-    final refresh = await storage.readRefreshToken();
+    final db = ref.read(localDbProvider);
+    final refresh = await db.read('refresh_token');
     if (refresh == null) {
       state = const AuthState(isLoggedIn: false, isLoading: false);
       return;
@@ -51,8 +51,8 @@ class AuthNotifier extends Notifier<AuthState> {
           .post('/api/auth/refresh', data: {'refreshToken': refresh});
       final data = response.data['data'];
       if (data != null) {
-        await storage.writeAccessToken(data['accessToken']);
-        await storage.writeRefreshToken(data['refreshToken']);
+        await db.write('access_token', data['accessToken']);
+        await db.write('refresh_token', data['refreshToken']);
         state = AuthState(
           isLoggedIn: true,
           isLoading: false,
@@ -128,8 +128,8 @@ class AuthNotifier extends Notifier<AuthState> {
   /// 登出
   Future<void> logout() async {
     final api = ref.read(apiClientProvider);
-    final storage = ref.read(secureStorageProvider);
-    final refresh = await storage.readRefreshToken();
+    final db = ref.read(localDbProvider);
+    final refresh = await db.read('refresh_token');
     if (refresh != null) {
       try { await api.post('/api/auth/logout', data: {'refreshToken': refresh}); } catch (_) {}
     }