add backend server setup with environment configuration, tile caching, and bus stop fetching functionality

lib/pages/map/routing/osrm_routing_service.dart

@@ -2,10 +2,11 @@ import 'dart:convert';
 
 import 'package:http/http.dart' as http;
 import 'package:latlong2/latlong.dart';
+import 'package:rra_app/pages/map/constants.dart';
 
 class OsrmRoutingService {
   const OsrmRoutingService({
-    this.baseUrl = 'https://router.project-osrm.org',
+    this.baseUrl = kBackendBaseUrl,
     this.profile = 'driving',
   });
 
@@ -21,8 +22,7 @@ class OsrmRoutingService {
         .map((point) => '${point.longitude},${point.latitude}')
         .join(';');
     final uri = Uri.parse(
-      '$baseUrl/route/v1/$profile/$coordinates'
-      '?overview=full&geometries=geojson',
+      '$baseUrl/route?waypoints=$coordinates&profile=$profile',
     );
 
     final response = await http.get(uri);