replaced account data singleton with a session model

lib/view/login/login.dart

@@ -4,6 +4,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 
 import '../../background/widget_background_task.dart';
+import '../../session/session_lifecycle.dart';
 import '../../state/app/modules/account/bloc/account_bloc.dart';
 import '../../state/app/modules/account/bloc/account_state.dart';
 import '../../state/app/modules/settings/bloc/settings_cubit.dart';
@@ -11,6 +12,7 @@ import '../../storage/dev_tools_settings.dart';
 import '../../storage/settings.dart' as model;
 import '../../theming/light_app_theme.dart';
 import '../../utils/haptics.dart';
+import '../../widget/info_dialog.dart';
 import '../pages/settings/widgets/endpoint_picker.dart';
 import 'login_controller.dart';
 import 'post_login_splash.dart';
@@ -34,6 +36,21 @@ class _LoginState extends State<Login> with SingleTickerProviderStateMixin {
     value: 1,
   );
 
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addPostFrameCallback((_) => _showSignOutNotice());
+  }
+
+  /// An involuntary sign-out (expired token, rotated password) otherwise just
+  /// drops the user here without a word.
+  void _showSignOutNotice() {
+    final notice = SessionLifecycle.signOutNotice.value;
+    if (notice == null || !mounted) return;
+    SessionLifecycle.signOutNotice.value = null;
+    InfoDialog.show(context, notice, title: 'Erneut anmelden');
+  }
+
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();