feat: 新增站内消息系统，支持通知与订单跳转

lib/app/app.dart

@@ -1,19 +1,67 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../core/app_keys.dart';
+import '../core/notifications/keep_alive.dart';
+import '../core/notifications/local_notifications.dart';
 import '../core/theme/app_theme.dart';
 import '../core/theme/app_typography.dart';
+import '../features/auth/application/session_controller.dart';
+import '../features/notice/application/notice_alert_controller.dart';
 import 'router.dart';
 
-class VoltLinkApp extends ConsumerWidget {
+class VoltLinkApp extends ConsumerStatefulWidget {
   const VoltLinkApp({super.key});
 
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
+  ConsumerState<VoltLinkApp> createState() => _VoltLinkAppState();
+}
+
+class _VoltLinkAppState extends ConsumerState<VoltLinkApp> {
+  StreamSubscription<String>? _tapSub;
+
+  @override
+  void initState() {
+    super.initState();
+    // 运行期点击系统通知 → 跳转对应页面
+    _tapSub = LocalNotifications.instance.taps.listen(_openRoute);
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      // 冷启动由通知拉起时，初始化阶段已把路由暂存下来
+      final route = LocalNotifications.instance.takeLaunchRoute();
+      if (route != null) _openRoute(route);
+      // 已登录则开启 Android 前台服务
+      unawaited(
+        BackgroundKeepAlive.setEnabled(ref.read(sessionProvider).isLoggedIn),
+      );
+    });
+  }
+
+  @override
+  void dispose() {
+    _tapSub?.cancel();
+    super.dispose();
+  }
+
+  void _openRoute(String route) {
+    if (!mounted || route.isEmpty) return;
+    ref.read(routerProvider).go(route);
+  }
+
+  @override
+  Widget build(BuildContext context) {
     final router = ref.watch(routerProvider);
 
+    // 登录/登出时同步 Android 前台服务开关
+    ref.listen(sessionProvider.select((s) => s.isLoggedIn), (_, loggedIn) {
+      unawaited(BackgroundKeepAlive.setEnabled(loggedIn));
+    });
+
+    // 激活站内消息提醒轮询
+    ref.watch(noticeAlertProvider);
+
     return MaterialApp.router(
       title: 'VoltLink',
       debugShowCheckedModeBanner: false,