perf: fast offline startup

close #511

lib/main.dart

@@ -36,6 +36,7 @@ import 'services/server_registry.dart';
 import 'services/download_manager_service.dart';
 import 'services/pip_service.dart';
 import 'services/download_storage_service.dart';
+import 'package:connectivity_plus/connectivity_plus.dart';
 import 'services/plex_api_cache.dart';
 import 'database/app_database.dart';
 import 'utils/app_logger.dart';
@@ -376,8 +377,14 @@ class _SetupScreenState extends State<SetupScreen> {
     final storage = await StorageService.getInstance();
     final registry = ServerRegistry(storage);
 
-    // Refresh servers from API to get updated connection info (IPs may change)
-    await registry.refreshServersFromApi();
+    // Check network connectivity early to fast-path airplane mode
+    final connectivityResult = await Connectivity().checkConnectivity();
+    final hasNetwork = !connectivityResult.contains(ConnectivityResult.none);
+
+    if (hasNetwork) {
+      // Refresh servers from API to get updated connection info (IPs may change)
+      await registry.refreshServersFromApi();
+    }
 
     // Load all configured servers
     final servers = await registry.getServers();
@@ -391,6 +398,17 @@ class _SetupScreenState extends State<SetupScreen> {
 
     if (!mounted) return;
 
+    // No network — skip connection attempts and go straight to offline mode
+    if (!hasNetwork) {
+      await context.read<DownloadProvider>().ensureInitialized();
+      if (!mounted) return;
+      Navigator.pushReplacement(
+        context,
+        MaterialPageRoute(builder: (context) => const MainScreen(isOfflineMode: true)),
+      );
+      return;
+    }
+
     try {
       final result = await ServerConnectionOrchestrator.connectAndInitialize(
         servers: servers,

lib/services/plex_auth_service.dart

@@ -51,7 +51,10 @@ class PlexAuthService {
 
   static Future<PlexAuthService> create() async {
     final storage = await StorageService.getInstance();
-    final dio = Dio();
+    final dio = Dio(BaseOptions(
+      connectTimeout: ConnectionTimeouts.plexTvConnect,
+      receiveTimeout: ConnectionTimeouts.plexTvReceive,
+    ));
 
     // Get or create client identifier
     String? clientIdentifier = storage.getClientIdentifier();

lib/utils/connection_constants.dart

@@ -17,4 +17,10 @@ class ConnectionTimeouts {
 
   /// Dio receive timeout for streaming/large responses from a Plex server.
   static const receive = Duration(seconds: 120);
+
+  /// Dio connect timeout for plex.tv / clients.plex.tv API requests.
+  static const plexTvConnect = Duration(seconds: 5);
+
+  /// Dio receive timeout for plex.tv / clients.plex.tv API responses.
+  static const plexTvReceive = Duration(seconds: 10);
 }