custom login implementation, period-based timetable layout with overlap handling, enhanced error dialogs, and unified bottom sheets

lib/main.dart

@@ -159,6 +159,15 @@ class _MainState extends State<Main> {
               themeMode: settings.appTheme,
               theme: LightAppTheme.theme,
               darkTheme: DarkAppTheme.theme,
+              // Brand-colored backdrop behind every route. During the logout
+              // home-swap and route pop animations the framework can briefly
+              // expose the layer below the topmost Scaffold; without this
+              // the dark Material default shows through and the user sees a
+              // black flash.
+              builder: (context, child) => ColoredBox(
+                color: LightAppTheme.marianumRed,
+                child: child ?? const SizedBox.shrink(),
+              ),
               home: LoaderOverlay(
                 child: Breaker(
                   breaker: BreakerArea.global,
@@ -203,14 +212,16 @@ class _MainState extends State<Main> {
                         case AccountStatus.loggedOut:
                           return const Login();
                         case AccountStatus.undefined:
-                          return const Scaffold(
-                            body: Center(
+                          return Scaffold(
+                            backgroundColor: LightAppTheme.marianumRed,
+                            body: const Center(
                               child: Column(
                                 mainAxisAlignment: MainAxisAlignment.center,
                                 children: [
-                                  AppProgressIndicator.large(),
+                                  AppProgressIndicator.large(color: Colors.white),
                                   SizedBox(height: 16),
-                                  Text('Konto wird geladen…'),
+                                  Text('Konto wird geladen…',
+                                      style: TextStyle(color: Colors.white)),
                                 ],
                               ),
                             ),
@@ -234,16 +245,19 @@ Future<void> _wipeUserState({
   required BreakerBloc breakerBloc,
 }) async {
   try {
-    final prefs = await SharedPreferences.getInstance();
-    await prefs.clear();
-    PaintingBinding.instance.imageCache.clear();
-    await settingsCubit.reset();
+    // Reset user-data blocs whose tree is no longer mounted after the
+    // home swap. We do NOT touch SettingsCubit here — its outer BlocBuilder
+    // wraps MaterialApp, so emit'ing a fresh state would tear down the
+    // freshly-mounted Login tree and leave the user with a blank screen
+    // (the MaterialApp.builder backdrop) until the next interaction.
     await Future.wait([
       timetableBloc.reset(),
       chatListBloc.reset(),
       chatBloc.reset(),
       breakerBloc.reset(),
     ]);
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.clear();
     await HydratedBloc.storage.clear();
     await const CacheView().clear();
   } catch (e, s) {