refactor: simplify configuration handling for CMS URL

- Removed CmsServerBaseUrl utility class and updated references to directly access GwUrl from configuration.
- Adjusted frontoffice-deployment.yaml to remove CmsInternalBaseUrl environment variable.
- Updated appsettings for staging and main environments to reflect the correct CMS service URLs.
- Ensured consistent handling of GwUrl in TokenNotificationService and AddGrpcServices methods.

k8s/staging/frontoffice-deployment.yaml

@@ -1,6 +1,5 @@
 ---
-# FrontOffice (Blazor Server) — staging. Server-side gRPC/SignalR to CMS: set CmsInternalBaseUrl to the
-# in-cluster Service URL so TLS is not terminated on a broken public chain (PartialChain).
+# FrontOffice (Blazor Server) staging.
 apiVersion: apps/v1
 kind: Deployment
 metadata:
@@ -29,8 +28,6 @@ spec:
           env:
             - name: ASPNETCORE_ENVIRONMENT
               value: "Staging"
-            - name: CmsInternalBaseUrl
-              value: "http://cms-svc:8080"
           resources:
             requests:
               memory: "256Mi"