Umstellung auf UTC Timestamp

lib/popups/accept_jobs_popup.dart

@@ -375,7 +375,7 @@ _sendAnswer(SharedMapReference mapReference, Job job, int item) async {
   message.ver = job.ver.toString();
   message.item = item;
   message.track = Track();
-  message.track.time = DateTime.now().toUtc().toIso8601String();
+  message.track.time = Util.toUnixMillisUtc(DateTime.now().toUtc());
   message.track.pos = FinTaskPos();
   message.track.pos!.lat = currentPosition != null ? currentPosition.latitude : 0.0;
   message.track.pos!.long = currentPosition != null ? currentPosition.longitude : 0.0;