migrated custom timetable events to Marianum-Connect and refactored push notification handling

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

@@ -63,6 +63,10 @@ class TalkSection extends StatelessWidget {
               Haptics.selection();
               final enabled = e ?? false;
               settings.val(write: true).notificationSettings.enabled = enabled;
+              // Turning off does NOT unregister: the device stays subscribed so
+              // silent sync pushes keep arriving; the message handler and iOS
+              // NSE suppress only the visible notification (via the mirrored
+              // flag). Enabling (re-)registers and ensures the OS permission.
               if (enabled) {
                 final messenger = ScaffoldMessenger.of(context);
                 unawaited(() async {
@@ -82,8 +86,6 @@ class TalkSection extends StatelessWidget {
                     );
                   }
                 }());
-              } else {
-                unawaited(PushRegistration().unregister());
               }
             },
           ),