feat: add an invisible startup screen

lib/features/connection/startup_screen.dart

@@ -0,0 +1,68 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:go_router/go_router.dart';
+
+import '../../data/sources/localiser/realtime_data_client.dart';
+import '../../data/sources/localiser/session_client.dart';
+import '../../providers.dart';
+
+class StartupScreen extends ConsumerStatefulWidget {
+  const StartupScreen({super.key});
+
+  @override
+  ConsumerState<StartupScreen> createState() => _StartupScreenState();
+}
+
+class _StartupScreenState extends ConsumerState<StartupScreen> {
+  @override
+  void initState() {
+    super.initState();
+    _bootstrap();
+  }
+
+  Future<void> _bootstrap() async {
+    final store = ref.read(credentialStoreProvider);
+
+    final config = await store.loadServer();
+    if (!mounted) return;
+
+    if (config == null) {
+      context.go('/connect');
+      return;
+    }
+
+    final creds = await store.load();
+    if (!mounted) return;
+
+    if (creds == null) {
+      context.go('/connect');
+      return;
+    }
+
+    try {
+      final tokenResponse =
+          await SessionClient(config: config).login(creds.username, creds.password);
+      if (!mounted) return;
+
+      final token = tokenResponse.token;
+      ref.read(serverConfigProvider.notifier).state = config;
+      ref.read(authTokenProvider.notifier).state = token;
+
+      final realtime = RealtimeDataClient(config: config, token: token);
+      await realtime.connect();
+      if (!mounted) return;
+
+      ref.read(realtimeDataClientProvider.notifier).state = realtime;
+      context.go('/floorplan');
+    } catch (_) {
+      if (mounted) context.go('/connect');
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return const Scaffold(
+      body: Center(child: CircularProgressIndicator()),
+    );
+  }
+}

lib/router.dart

@@ -30,6 +30,10 @@ final routerProvider = Provider<GoRouter>((ref) {
       return null;
     },
     routes: [
+      GoRoute(
+        path: '/',
+        builder: (context, state) => const StartupScreen(),
+      ),
       GoRoute(
         path: '/connect',
         builder: (context, state) => const ServerDiscoveryScreen(),