replaced account data singleton with a session model

lib/view/pages/settings/sections/account_section.dart

@@ -4,10 +4,10 @@ import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 
 import '../../../../api/marianumcloud/cloud_users/cloud_users_actions.dart';
-import '../../../../api/marianumconnect/queries/auth_logout/auth_logout.dart';
-import '../../../../model/account_data.dart';
 import '../../../../push/push_registration.dart';
 import '../../../../routing/app_routes.dart';
+import '../../../../session/session_lifecycle.dart';
+import '../../../../session/session_manager.dart';
 import '../../../../state/app/modules/account/bloc/account_bloc.dart';
 import '../../../../state/app/modules/account/bloc/account_state.dart';
 import '../../../../widget/app_progress_indicator.dart';
@@ -84,13 +84,17 @@ class _AccountSectionState extends State<AccountSection> {
     setState(() => _avatarBusy = false);
     if (!ok) return;
 
-    invalidateAvatarCache(id: AccountData().getUsername(), isGroup: false);
+    invalidateAvatarCache(
+      id: SessionManager().requireNextcloud().username,
+      isGroup: false,
+    );
     setState(() => _avatarVersion++);
   }
 
   @override
   Widget build(BuildContext context) {
-    final username = AccountData().getUsername();
+    final nextcloud = SessionManager().requireNextcloud();
+    final username = nextcloud.username;
     final displayName = _displayName;
     final theme = Theme.of(context);
 
@@ -175,7 +179,7 @@ class _AccountSectionState extends State<AccountSection> {
         // Nur für Login-Flow-Konten (2FA) sichtbar — Passwort-Konten heilen
         // sich still über das App-Passwort-Minting und sollen von dem ganzen
         // Flow-Mechanismus nichts mitbekommen.
-        if (!AccountData().isDemo && AccountData().usesLoginFlow)
+        if (!SessionManager().isDemo && nextcloud.usesLoginFlow)
           AsyncListTile(
             leading: const Icon(Icons.cloud_sync_outlined),
             title: const Text('Nextcloud neu verbinden'),
@@ -203,7 +207,7 @@ class _AccountSectionState extends State<AccountSection> {
 
   Future<void> _showLogoutDialog(BuildContext context) async {
     // Flip AccountBloc state only after the dialog fully closes: doing it from
-    // inside removeData (the previous approach) raced AsyncDialogAction's
+    // inside the sign-out (the previous approach) raced AsyncDialogAction's
     // pop(true) against the listener's popUntil(isFirst) and could leave the
     // navigator in an inconsistent state.
     final confirmed = await showDialog<bool>(
@@ -219,14 +223,8 @@ class _AccountSectionState extends State<AccountSection> {
     context.read<AccountBloc>().setStatus(AccountStatus.loggedOut);
   }
 
-  // Ordered teardown: unregister push at Nextcloud + proxy and revoke the app
-  // password (while Nextcloud credentials are still available), THEN revoke the
-  // MC bearer token, and finally wipe local credentials. Each step is
-  // best-effort so an offline logout still reaches a clean local state.
   Future<void> _performLogout() async {
-    await PushRegistration().logoutCleanup();
-    await AuthLogout().run();
-    await AccountData().removeData();
+    await SessionLifecycle.signOut();
     _cachedDisplayName = null;
   }
 }