chore: enhance configuration for gateway URL handling

- Added GW_URL and GwUrl environment variables in frontoffice-deployment.yaml and Dockerfile for consistent gateway URL configuration.
- Updated AddGrpcServices method to resolve gateway URL from both environment variables, ensuring proper error handling for missing values.
- Modified TokenNotificationService to prioritize GW_URL over GwUrl for improved configuration flexibility.

src/FrontOffice.Main/Utilities/TokenNotificationService.cs

@@ -69,7 +69,7 @@ public class TokenNotificationService : IAsyncDisposable
                 return;
             }
 
-            var gwUrl = _configuration["GwUrl"]?.TrimEnd('/') ?? "https://localhost:5002";
+            var gwUrl = (_configuration["GW_URL"] ?? _configuration["GwUrl"])?.TrimEnd('/') ?? "https://localhost:5002";
             var hubPath = _configuration["SignalR:HubPath"] ?? "/hubs/token-relay";
             var hubUrl = $"{gwUrl}{hubPath}";