upgrade to target sdk 34: mark OngoingNotificationsService as Special Use, register receivers as exported

(This is required because it is allowed that plugins send intents and also intents from system notifications are not received in NonExported mode)

src/keepass2android-app/QuickUnlock.cs

@@ -153,7 +153,7 @@ namespace keepass2android
 			_intentReceiver = new QuickUnlockBroadcastReceiver(this);
 			IntentFilter filter = new IntentFilter();
 			filter.AddAction(Intents.DatabaseLocked);
-			RegisterReceiver(_intentReceiver, filter);
+			RegisterReceiver(_intentReceiver, filter, ReceiverFlags.Exported);
 
             Util.SetNoPersonalizedLearning(FindViewById<EditText>(Resource.Id.QuickUnlock_password));
 
@@ -503,8 +503,6 @@ namespace keepass2android
 				}
 			}
 		}
-
-
 	}
 }