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.

k8s/staging/frontoffice-deployment.yaml

@@ -28,6 +28,10 @@ spec:
           env:
             - name: ASPNETCORE_ENVIRONMENT
               value: "Staging"
+            - name: GW_URL
+              value: "https://cms.se.kbs1.ir"
+            - name: GwUrl
+              value: "https://cms.se.kbs1.ir"
           resources:
             requests:
               memory: "256Mi"