Phase 1 #24: Flutter 移动端框架（三合一 APP 骨架）

- pubspec.yaml: dio/provider/shared_preferences/flutter_map/geolocator
- main.dart: Provider 状态管理 + 登录守卫
- AuthService: Token 管理 + Dio HTTP + SharedPreferences 持久化
- LoginPage: Material Design 登录页
- HomePage: 三合一 BottomTab 导航（供水/巡检/营收）
- 预留依赖: flutter_local_notifications/image_picker/permission_handler

mobile/lib/main.dart

@@ -0,0 +1,25 @@
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+import 'services/auth_service.dart';
+import 'pages/login/login_page.dart';
+import 'pages/home/home_page.dart';
+
+void main() => runApp(const WaterApp());
+
+class WaterApp extends StatelessWidget {
+  const WaterApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MultiProvider(
+      providers: [ChangeNotifierProvider(create: (_) => AuthService())],
+      child: MaterialApp(
+        title: '智慧水务',
+        theme: ThemeData(primarySwatch: Colors.blue, useMaterial3: true),
+        home: Consumer<AuthService>(
+          builder: (_, auth, __) => auth.isLoggedIn ? const HomePage() : const LoginPage(),
+        ),
+      ),
+    );
+  }
+}