feat(client): 记住上次选择的节点 + 自动连接 toast(1.0.24)

- selectedNodeCodeProvider 改为持久化 StateNotifier(select() 落盘、启动恢复,默认智能 AUTO);
  自动连接复用上次选择:智能就智能、具体就具体。
- 自动连接门控加等「选中节点已恢复」(controller.loaded),避免用到未恢复的默认值。
- 自动连接触发时弹 toast「正在自动连接到 X」(全局 ScaffoldMessenger key)。
- 测试:选中节点 select 落盘 + 重启恢复(具体/智能)。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/main.dart

@@ -23,6 +23,9 @@ import 'widgets/auth_screen.dart';
 import 'widgets/onboarding_screen.dart';
 import 'widgets/pangolin_logo.dart';
 
+/// 全局 ScaffoldMessenger key:供无 BuildContext 处(如自动连接)弹 SnackBar/toast。
+final rootMessengerKey = GlobalKey<ScaffoldMessengerState>();
+
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
   // 桌面端:单实例 + 常驻系统托盘(关闭窗口隐藏到托盘而非退出)。
@@ -98,6 +101,7 @@ class _PangolinAppState extends ConsumerState<PangolinApp> {
     final mode = ref.watch(themeModeProvider);
     return MaterialApp(
       title: '穿山甲',
+      scaffoldMessengerKey: rootMessengerKey,
       debugShowCheckedModeBanner: false,
       theme: PangolinTheme.light,
       darkTheme: PangolinTheme.dark,
@@ -131,22 +135,33 @@ class _RootFlowState extends ConsumerState<RootFlow> {
     logLine('AutoConnect', 'armed; waiting for settings loaded + nodes ready');
     ProviderSubscription<AsyncValue<List<Node>>>? nodeSub;
     ProviderSubscription<AppSettings>? settingsSub;
+    ProviderSubscription<String>? selSub;
     var decided = false;
     void tryGo() {
       if (decided) return;
       final settings = ref.read(settingsProvider);
+      final selLoaded = ref.read(selectedNodeCodeProvider.notifier).loaded;
       // 直接判 _connect 实际会用的「生效节点」是否就绪(uuid 非空),而非「列表里有任一就绪节点」——
       // 否则可能在 effectiveNode 尚是占位/未就绪时就触发,_connect 报「节点尚未就绪」。
+      // 还要等设置 + 选中节点都从持久化恢复完,否则可能用到未恢复的默认(智能)而非上次选择。
       final node = ref.read(effectiveNodeProvider);
-      if (!settings.loaded || node.uuid.isEmpty) return;
+      if (!settings.loaded || !selLoaded || node.uuid.isEmpty) return;
       decided = true;
       nodeSub?.close();
       settingsSub?.close();
+      selSub?.close();
       final phase = ref.read(connectionProvider).phase;
       logLine('AutoConnect', 'ready: autoConnect=${settings.autoConnect} phase=$phase node=${node.code} uuid=${node.uuid.isEmpty ? "EMPTY" : "ok"}');
       if (settings.autoConnect && phase == VpnPhase.off) {
-        logLine('AutoConnect', 'triggering connect');
+        logLine('AutoConnect', 'triggering connect → ${node.code}');
         ref.read(connectionProvider.notifier).toggle();
+        // 自动连接 toast:告知用户「正在自动连接到 X」。
+        final t = ref.read(appTextProvider);
+        rootMessengerKey.currentState?.showSnackBar(SnackBar(
+          content: Text(t.autoConnectingTo(node.localizedName(t.lang))),
+          behavior: SnackBarBehavior.floating,
+          duration: const Duration(seconds: 3),
+        ));
       } else {
         logLine('AutoConnect', 'NOT connecting (autoConnect=${settings.autoConnect} phase=$phase)');
       }
@@ -154,6 +169,7 @@ class _RootFlowState extends ConsumerState<RootFlow> {
 
     nodeSub = ref.listenManual(nodesProvider, (_, __) => tryGo());
     settingsSub = ref.listenManual(settingsProvider, (_, __) => tryGo());
+    selSub = ref.listenManual(selectedNodeCodeProvider, (_, __) => tryGo());
     tryGo();
   }