implemented post-login splash screen with Lottie animations and integrated background data prefetching during the login transition

lib/main.dart

@@ -41,6 +41,7 @@ import 'theming/dark_app_theme.dart';
 import 'theming/light_app_theme.dart';
 import 'utils/app_paths.dart';
 import 'view/login/login.dart';
+import 'view/login/post_login_splash.dart';
 import 'widget/app_progress_indicator.dart';
 import 'widget/breaker/breaker.dart';
 import 'widget/debug/cache_view.dart';
@@ -188,6 +189,9 @@ class Main extends StatefulWidget {
 }
 
 class _MainState extends State<Main> {
+  bool _showPostLoginSplash = false;
+  bool _appMounted = true;
+
   @override
   void initState() {
     super.initState();
@@ -215,6 +219,12 @@ class _MainState extends State<Main> {
   /// password has been rotated server-side; the validator wipes the local
   /// session and we flip the account bloc back to `loggedOut`, which sends
   /// the user to the login screen.
+  void _prefetchBaseData(BuildContext context) {
+    context.read<TimetableBloc>().refresh();
+    unawaited(context.read<ChatListBloc>().refresh(silent: true));
+    unawaited(ListFilesCache.prefetchRootListing());
+  }
+
   void _scheduleSessionValidation(AccountBloc accountBloc) {
     unawaited(
       SessionValidator.probeStored(
@@ -282,6 +292,12 @@ class _MainState extends State<Main> {
                     unawaited(
                       context.read<NextcloudCapabilitiesCubit>().load(),
                     );
+                    _showPostLoginSplash = true;
+                    _appMounted = false;
+                    WidgetsBinding.instance.addPostFrameCallback((_) {
+                      if (mounted) setState(() => _appMounted = true);
+                    });
+                    _prefetchBaseData(context);
                   }
                   if (accountState.status != AccountStatus.loggedOut) return;
                   // A pending share would otherwise survive logout and be
@@ -328,7 +344,19 @@ class _MainState extends State<Main> {
                 builder: (context, accountState) {
                   switch (accountState.status) {
                     case AccountStatus.loggedIn:
-                      return const App();
+                      return Stack(
+                        fit: StackFit.expand,
+                        children: [
+                          if (_appMounted) const App(key: ValueKey('app-shell')),
+                          if (_showPostLoginSplash)
+                            PostLoginSplash(
+                              key: const ValueKey('post-login-splash'),
+                              onComplete: () => setState(
+                                () => _showPostLoginSplash = false,
+                              ),
+                            ),
+                        ],
+                      );
                     case AccountStatus.loggedOut:
                       return const Login();
                     case AccountStatus.undefined: