replaced account data singleton with a session model

lib/api/marianumconnect/queries/timetable_custom_events/custom_events_migration.dart

@@ -2,8 +2,8 @@ import 'dart:developer';
 
 import 'package:shared_preferences/shared_preferences.dart';
 
-import '../../../../model/account_data.dart';
-import '../../../demo/demo_mode.dart';
+import '../../../../session/session.dart';
+import '../../../../session/session_manager.dart';
 import '../../../mhsl/custom_timetable_event/get/get_custom_timetable_event.dart';
 import '../../../mhsl/custom_timetable_event/get/get_custom_timetable_event_params.dart';
 import '../../../mhsl/custom_timetable_event/remove/remove_custom_timetable_event.dart';
@@ -26,28 +26,32 @@ class CustomEventsMigration {
   const CustomEventsMigration._();
 
   static Future<void> runOnce() async {
-    if (DemoMode.active) return;
+    // Only password accounts can derive the legacy identity.
+    final session = SessionManager().current;
+    if (session is! CredentialSession || session.isDemo) return;
     if (await _isDone()) return;
 
-    final epoch = AccountData().sessionEpoch;
+    final epoch = SessionManager().sessionEpoch;
     try {
       final response = await GetCustomTimetableEvent(
-        GetCustomTimetableEventParams(AccountData().getUserSecret()),
+        GetCustomTimetableEventParams(session.legacyUserSecret),
       ).run();
 
       for (final event in response.events) {
         // The POST authenticates with whoever is signed in now; after a
         // sign-out the previous account's events would land in the next one.
-        if (!AccountData().isCurrentSession(epoch)) return;
+        if (!SessionManager().isCurrentSession(epoch)) return;
         await TimetableCustomEventsAdd().run(event);
         await RemoveCustomTimetableEvent(
           RemoveCustomTimetableEventParams(event.id),
         ).run();
       }
 
-      if (!AccountData().isCurrentSession(epoch)) return;
+      if (!SessionManager().isCurrentSession(epoch)) return;
       await _markDone();
-      log('Custom events migration: moved ${response.events.length} event(s) to Marianum-Connect.');
+      log(
+        'Custom events migration: moved ${response.events.length} event(s) to Marianum-Connect.',
+      );
     } catch (e) {
       // Leave the flag unset so the next launch retries; the delete-after-post
       // above keeps a partial run duplicate-free.