feat(samples): Show splash while authenticating

sample_app/lib/app/content/auth_controller.dart

@@ -23,6 +23,8 @@ class AuthController extends ValueNotifier<AuthState> {
   PushTokenManager? _pushTokenManager;
 
   Future<void> connect(UserCredentials credentials) async {
+    value = const Authenticating();
+
     final token = UserToken(credentials.token);
 
     final client = StreamFeedsClient(
@@ -83,3 +85,7 @@ final class Authenticated extends AuthState {
 final class Unauthenticated extends AuthState {
   const Unauthenticated();
 }
+
+final class Authenticating extends AuthState {
+  const Authenticating();
+}

sample_app/lib/navigation/app_router.dart

@@ -7,6 +7,7 @@ import 'package:stream_feeds/stream_feeds.dart';
 import '../screens/choose_user/choose_user_screen.dart';
 import '../screens/home/home_screen.dart';
 import '../screens/user_feed/user_feed_screen.dart';
+import '../widgets/app_splash.dart';
 import '../widgets/attachment_gallery/attachment_gallery.dart';
 import '../widgets/attachment_gallery/attachment_metadata.dart';
 import 'guards/auth_guard.dart';
@@ -45,6 +46,11 @@ class AppRouter extends RootStackRouter {
         page: ChooseUserRoute.page,
         keepHistory: false,
       ),
+      AutoRoute(
+        path: '/loading',
+        page: AppSplashRoute.page,
+        keepHistory: false,
+      ),
       AutoRoute(
         path: '/attachment_gallery',
         page: AttachmentGalleryRoute.page,

sample_app/lib/navigation/guards/auth_guard.dart

@@ -15,6 +15,12 @@ class AuthGuard extends AutoRouteGuard {
     final isAuthenticated = _authController.value is Authenticated;
     // If the user is authenticated, allow navigation to the requested route.
     if (isAuthenticated) return resolver.next();
+
+    // If the user is being authenticated, show the splash screen.
+    if (_authController.value is Authenticating) {
+      resolver.redirectUntil(const AppSplashRoute(), replace: true);
+    }
+
     // Otherwise, redirect to the Choose user page.
     resolver.redirectUntil(const ChooseUserRoute(), replace: true);
   }

sample_app/lib/widgets/app_splash.dart

@@ -1,3 +1,4 @@
+import 'package:auto_route/auto_route.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_svg/flutter_svg.dart';
 
@@ -7,6 +8,7 @@ import '../theme/theme.dart';
 ///
 /// Displays only the app logo in a clean, minimal style while the app initializes.
 /// Follows true minimalistic principles with perfect simplicity.
+@RoutePage(name: 'AppSplashRoute')
 class AppSplash extends StatelessWidget {
   const AppSplash({super.key});