replaced account data singleton with a session model

lib/view/login/account_loading_screen.dart

@@ -2,7 +2,7 @@ import 'dart:async';
 
 import 'package:flutter/material.dart';
 
-import '../../model/account_data.dart';
+import '../../session/session_manager.dart';
 import '../../theming/light_app_theme.dart';
 import '../../widget/app_progress_indicator.dart';
 
@@ -61,7 +61,7 @@ class _AccountLoadingScreenState extends State<AccountLoadingScreen> {
               ),
               const SizedBox(height: 8),
               TextButton(
-                onPressed: AccountData().abandonLoad,
+                onPressed: SessionManager().abandonLoad,
                 style: TextButton.styleFrom(foregroundColor: Colors.white),
                 child: const Text('Zur Anmeldung'),
               ),

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();

lib/view/login/login_controller.dart

@@ -10,8 +10,9 @@ import '../../api/marianumconnect/auth/device_token_name.dart';
 import '../../api/marianumconnect/auth/token_storage.dart';
 import '../../api/marianumconnect/queries/auth_login/auth_login.dart';
 import '../../api/marianumconnect/queries/auth_logout/auth_logout.dart';
-import '../../model/account_data.dart';
 import '../../model/session_wipe.dart';
+import '../../session/session.dart';
+import '../../session/session_manager.dart';
 import '../../widget_data/widget_sync.dart';
 
 /// Outcome of a login attempt.
@@ -56,25 +57,18 @@ class LoginController extends ChangeNotifier {
     // Demo login: the prefix enters local demo mode, password ignored, no
     // network (see DemoMode).
     if (DemoMode.matches(user)) {
-      await AccountData().removeData();
-      await const MarianumConnectTokenStorage().clear();
-      await WidgetSync.clear();
-      await WidgetSync.triggerUpdate();
-      await AccountData().setDemo(user);
+      await _discardPreviousAccount();
+      await SessionManager().signIn(
+        CredentialSession(username: user, password: 'demo', isDemo: true),
+      );
       _loading = false;
       notifyListeners();
       return LoginResult.success;
     }
 
+    var signedIn = false;
     try {
-      await AccountData().removeData();
-      // Vorherigen Token revoken bevor wir einen neuen anfordern — ein altes
-      // Account hätte sonst noch einen aktiven Token in api_tokens.
-      await const MarianumConnectTokenStorage().clear();
-      // Widget-Snapshot löschen, sonst blitzt nach Account-Wechsel kurz der
-      // Stundenplan des vorigen Users auf dem Home-Bildschirm.
-      await WidgetSync.clear();
-      await WidgetSync.triggerUpdate();
+      await _discardPreviousAccount();
       // AuthLogin = Credential-Probe + Token-Create in einem Call.
       // 401 hier heißt: falsches Passwort.
       await AuthLogin().run(
@@ -82,7 +76,10 @@ class LoginController extends ChangeNotifier {
         password: password,
         tokenName: await DeviceTokenName.resolve(),
       );
-      await AccountData().setData(user, password);
+      await SessionManager().signIn(
+        CredentialSession(username: user, password: password),
+      );
+      signedIn = true;
       // Mint the Nextcloud app password now — it doubles as the Nextcloud
       // credential probe: a rejection means 2FA is active (or the NC password
       // diverges) and the login must finish interactively in the browser.
@@ -92,7 +89,9 @@ class LoginController extends ChangeNotifier {
       return ncReady ? LoginResult.success : LoginResult.nextcloudLoginRequired;
     } catch (e) {
       log(e.toString());
-      await AccountData().removeData();
+      // Only the account signed in by this attempt; while adding an account
+      // the active one is parked and restored on cancel.
+      if (signedIn) await SessionManager().signOut();
       await const MarianumConnectTokenStorage().clear();
       final isWrongCredentials = e is AuthException && e.statusCode == 401;
       _errorMessage = isWrongCredentials
@@ -105,6 +104,17 @@ class LoginController extends ChangeNotifier {
     }
   }
 
+  /// Vorherigen Token verwerfen, bevor ein neuer angefordert wird, und den
+  /// Widget-Snapshot löschen — sonst blitzt nach einem Account-Wechsel kurz
+  /// der Stundenplan des vorigen Users auf dem Home-Bildschirm. Die Session
+  /// selbst überschreibt signIn vollständig; beim Hinzufügen eines Kontos
+  /// liegt der Token des aktiven Kontos schon in dessen Tresor.
+  Future<void> _discardPreviousAccount() async {
+    await const MarianumConnectTokenStorage().clear();
+    await WidgetSync.clear();
+    await WidgetSync.triggerUpdate();
+  }
+
   /// Tries to mint the Nextcloud app password with the just-verified password.
   /// `false` = Nextcloud rejected the credentials → Login Flow v2 required.
   /// Transport/server problems stay non-blocking (like the previous
@@ -112,7 +122,7 @@ class LoginController extends ChangeNotifier {
   Future<bool> _prepareNextcloudAppPassword() async {
     try {
       final appPassword = await GetAppPassword().run();
-      await AccountData().setAppPassword(appPassword);
+      await SessionManager().setAppPassword(appPassword);
       return true;
     } on AuthException {
       return false;
@@ -131,7 +141,7 @@ class LoginController extends ChangeNotifier {
     } on Object catch (e) {
       log('Login rollback: MC logout failed: $e');
     }
-    await AccountData().removeData();
+    await SessionManager().signOut();
     await const MarianumConnectTokenStorage().clear();
     _errorMessage =
         'Die Anmeldung wurde abgebrochen — dein Konto erfordert die Bestätigung im Browser.';

lib/view/login/nextcloud_login_flow_page.dart

@@ -7,7 +7,7 @@ import 'package:flutter/material.dart';
 import '../../api/errors/error_mapper.dart';
 import '../../api/marianumcloud/app_password/delete_app_password.dart';
 import '../../api/marianumcloud/login_flow/login_flow_api.dart';
-import '../../model/account_data.dart';
+import '../../session/session_manager.dart';
 import '../../utils/url_opener.dart';
 import '../../widget/app_progress_indicator.dart';
 
@@ -19,7 +19,7 @@ enum _FlowStep { primary, talk }
 
 /// Runs the Nextcloud Login Flow v2: opens the browser login, polls until the
 /// user confirmed it there (2FA happens inside the browser) and adopts the
-/// returned app password via [AccountData.setLoginFlow]. A second, skippable
+/// returned app password via [SessionManager.setLoginFlow]. A second, skippable
 /// pass mints the Talk app password so flow accounts keep BOTH push
 /// subscriptions (see PushRegistrationType). Pops `true` once the primary
 /// credential was adopted, `false`/`null` when the user backs out before that.
@@ -104,7 +104,7 @@ class _NextcloudLoginFlowPageState extends State<NextcloudLoginFlowPage>
       final credentials = await _api.poll(flow);
       if (credentials == null || _finished || !mounted) return;
       if (!LoginFlowApi.loginNameMatches(
-        expected: AccountData().getUsername(),
+        expected: SessionManager().requireNextcloud().username,
         actual: credentials.loginName,
       )) {
         _timer?.cancel();
@@ -120,7 +120,7 @@ class _NextcloudLoginFlowPageState extends State<NextcloudLoginFlowPage>
       }
       switch (_step) {
         case _FlowStep.primary:
-          await AccountData().setLoginFlow(credentials.appPassword);
+          await SessionManager().setLoginFlow(credentials.appPassword);
           if (!mounted) return;
           // Zweite Freigabe direkt anstoßen: die Browser-Session besteht
           // bereits, es fehlt nur noch der Grant-Tipp.
@@ -129,7 +129,7 @@ class _NextcloudLoginFlowPageState extends State<NextcloudLoginFlowPage>
         case _FlowStep.talk:
           _finished = true;
           _timer?.cancel();
-          await AccountData().setAppPasswordTalk(credentials.appPassword);
+          await SessionManager().setAppPasswordTalk(credentials.appPassword);
           if (!mounted) return;
           Navigator.of(context).pop(true);
       }