feat: add main app entry with flutter hooks

lib/main.dart

@@ -1,19 +1,70 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_hooks/flutter_hooks.dart';
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'config/theme.dart';
+import 'services/api_service.dart';
+import 'services/background_service.dart';
+import 'screens/login_screen.dart';
+import 'screens/apps_screen.dart';
 
-void main() {
-  runApp(const MainApp());
+void main() async {
+  WidgetsFlutterBinding.ensureInitialized();
+
+  const storage = FlutterSecureStorage();
+  final savedUrl = await storage.read(key: 'server_url');
+  final savedToken = await storage.read(key: 'auth_token');
+
+  final api = ApiService(baseUrl: savedUrl ?? 'https://localhost');
+
+  if (savedToken != null) {
+    api.setToken(savedToken);
+  }
+
+  final bgService = BackgroundService();
+  await bgService.initialize();
+  await bgService.schedulePeriodicCheck();
+
+  runApp(UpdateForgeApp(api: api, hasToken: savedToken != null));
 }
 
-class MainApp extends StatelessWidget {
-  const MainApp({super.key});
+class UpdateForgeApp extends HookWidget {
+  final ApiService api;
+  final bool hasToken;
+
+  const UpdateForgeApp({super.key, required this.api, required this.hasToken});
 
   @override
   Widget build(BuildContext context) {
-    return const MaterialApp(
-      home: Scaffold(
-        body: Center(
-          child: Text('Hello World!'),
-        ),
+    final loggedIn = useState(hasToken && api.isAuthenticated);
+
+    Future<void> saveCredentials() async {
+      const storage = FlutterSecureStorage();
+      await storage.write(key: 'server_url', value: api.baseUrl);
+      await storage.write(key: 'auth_token', value: api.token);
+    }
+
+    Future<void> clearCredentials() async {
+      const storage = FlutterSecureStorage();
+      await storage.delete(key: 'auth_token');
+      api.setToken('');
+      loggedIn.value = false;
+    }
+
+    return MaterialApp(
+      title: 'UpdateForge',
+      theme: buildAppTheme(),
+      debugShowCheckedModeBanner: false,
+      home: loggedIn.value
+          ? AppsScreen(
+              api: api,
+              onLogout: clearCredentials,
+            )
+          : LoginScreen(
+              api: api,
+              onLogin: () async {
+                await saveCredentials();
+                loggedIn.value = true;
+              },
             ),
     );
   }