improved push notification settings with health indicators and optimized notification dismissal

lib/utils/downloads/download_manager.dart

@@ -179,6 +179,29 @@ class DownloadManager {
     final taskId = job.taskId;
     if (taskId == null || !Platform.isAndroid) return;
     final id = _androidNotificationId(taskId);
+    // background_downloader pushes the completion status to us *before* it posts
+    // the "Fertig" notification, and that post runs through a queue throttled to
+    // one notification per ~300ms. When the file opens immediately (lone
+    // foreground download), our first cancel therefore races ahead of the
+    // notification actually appearing and no-ops — leaving it stuck. Re-cancel
+    // across the throttle window so the notification is caught once it lands.
+    for (final delay in _dismissRetryDelays) {
+      if (delay == Duration.zero) {
+        _cancelNotification(id);
+      } else {
+        Future<void>.delayed(delay, () => _cancelNotification(id));
+      }
+    }
+  }
+
+  static const _dismissRetryDelays = [
+    Duration.zero,
+    Duration(milliseconds: 350),
+    Duration(milliseconds: 750),
+    Duration(milliseconds: 1500),
+  ];
+
+  void _cancelNotification(int id) {
     unawaited(
       NotificationService().flutterLocalNotificationsPlugin
           .cancel(id: id)