replaced account data singleton with a session model

lib/app.dart

@@ -10,7 +10,6 @@ import 'api/marianumconnect/marianumconnect_api.dart';
 import 'api/marianumconnect/queries/get_breakers/get_breakers_response.dart';
 import 'api/marianumconnect/queries/telemetry_heartbeat/telemetry_heartbeat.dart';
 import 'main.dart';
-import 'model/account_data.dart';
 import 'model/data_cleaner.dart';
 import 'notification/notification_controller.dart';
 import 'notification/notification_service.dart';
@@ -18,6 +17,7 @@ import 'notification/notification_tasks.dart';
 import 'push/push_registration.dart';
 import 'push/push_tap_router.dart';
 import 'routing/app_routes.dart';
+import 'session/session_manager.dart';
 import 'share_intent/share_intent_listener.dart';
 import 'state/app/modules/app_modules.dart';
 import 'state/app/modules/breaker/bloc/breaker_bloc.dart';
@@ -174,7 +174,7 @@ class _AppState extends State<App> with WidgetsBindingObserver {
       _timetableWidgetSync = timetable.stream.listen((state) {
         final data = state.data;
         if (data is TimetableState && !state.isLoading) {
-          final epoch = AccountData().sessionEpoch;
+          final epoch = SessionManager().sessionEpoch;
           Debouncer.debounce(
             'widgetPublish',
             const Duration(seconds: 1),
@@ -194,7 +194,7 @@ class _AppState extends State<App> with WidgetsBindingObserver {
       // frames are done (a fresh bloc emit in the meantime supersedes it).
       final initialData = timetable.state.data;
       if (initialData is TimetableState) {
-        final epoch = AccountData().sessionEpoch;
+        final epoch = SessionManager().sessionEpoch;
         Debouncer.debounce(
           'widgetPublish',
           const Duration(seconds: 3),