add backgroudapp bar color

lib/helper/config.dart

+import 'package:flutter/material.dart';
 import 'package:second_display/main.dart';
 import 'package:second_display/models/orders.dart';
 
 // final Color textColor = Colors.white;
 // final Color colorBackgroundOrder = Colors.black.withOpacity(0.8);
 final String? baseUrls = prefs.getString('base_url');
-final String urlDefault = '';
+const String urlDefault = '';
 late String baseUrl = baseUrls ?? urlDefault;
 final String getOrdersUrl = baseUrl + "midware/order/get_by_id";
-final String apiUrlConfig = "queue/config_second_display";
+const String apiUrlConfig = "queue/config_second_display";
 final String getJsonUrl = baseUrl + "midware/order/get_for_second_display";
 late CustomerOrders modelCustomerOrder = CustomerOrders(
     id: "",
@@ -24,3 +25,4 @@ late CustomerOrders modelCustomerOrder = CustomerOrders(
 
 final List<String>? imgLists = prefs.getStringList('imageList');
 final List<String> imglist = imgLists!;
+final Color? backgroundAppBar = Colors.indigo[900];