GNSS szervíz refraktorálás, hibajavítás, PhoneGpsConnection osztály

lib/services/gnss/gnss_device_service.dart

@@ -4,7 +4,7 @@ import 'package:flutter_blue_plus/flutter_blue_plus.dart';
 import 'package:get/get.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
-enum GnssConnectionType { btSerial, ble, phoneGps }
+enum GnssConnectionType { none, btSerial, ble, phoneGps }
 
 class GnssDevice {
   final String address;
@@ -23,6 +23,7 @@ class GnssDevice {
         GnssConnectionType.btSerial => 'BT Serial',
         GnssConnectionType.ble => 'BLE',
         GnssConnectionType.phoneGps => 'Telefon GPS',
+        GnssConnectionType.none => 'Kikapcsolva',
       };
 
   Map<String, dynamic> toJson() => {