fixed guardian login edge cases and misleading placeholders on failed loads

lib/push/notification_permission_prompt.dart

@@ -141,6 +141,10 @@ Future<void> _maybePrompt(
     if (prompt.spentOnDisplay) {
       prompt.markShown(settings.val(write: true).notificationSettings);
     }
+    // The OS prompt (and its "declined" follow-up) outlive this dialog, so
+    // hold on to them: releasing the guard at the dialog's close would let a
+    // second occasion stack another dialog over the pending OS prompt.
+    Future<void>? permissionRequest;
     await showDialog<void>(
       context: context,
       builder: ConfirmDialog(
@@ -150,9 +154,10 @@ Future<void> _maybePrompt(
         confirmButton: 'Weiter',
         cancelButton: null,
         onConfirm: () =>
-            unawaited(_requestPermission(context, settings, prompt)),
+            permissionRequest = _requestPermission(context, settings, prompt),
       ).build,
     );
+    await permissionRequest;
   } finally {
     _promptInFlight = false;
   }