added base homescreen-widget setup, working on Android, iOS in progress

lib/view/login/login_controller.dart

@@ -7,6 +7,7 @@ import '../../api/errors/error_mapper.dart';
 import '../../api/marianumcloud/talk/room/get_room.dart';
 import '../../api/marianumcloud/talk/room/get_room_params.dart';
 import '../../model/account_data.dart';
+import '../../widget_data/widget_sync.dart';
 
 /// Owns the login flow's transient state (loading, last error) so it can be
 /// driven from a thin Stateful view and unit-tested without a widget tree.
@@ -31,6 +32,11 @@ class LoginController extends ChangeNotifier {
     final user = username.trim().toLowerCase();
     try {
       await AccountData().removeData();
+      // Drop any cached widget snapshot from a previous account before the
+      // new credentials populate it — otherwise a re-login with a different
+      // user briefly shows the previous owner's timetable on the home screen.
+      await WidgetSync.clear();
+      await WidgetSync.triggerUpdate();
       await AccountData().setData(user, password);
       await GetRoom(GetRoomParams(includeStatus: false)).run();
       _loading = false;