fix: remove hardcoded GW_URL from Dockerfile and staging manifest

GW_URL/GwUrl env vars were baked into the Dockerfile (ENV) and the
staging K8s manifest, overriding appsettings.*.json at runtime.
This meant merging to production still used the staging CMS URL.

Now only ASPNETCORE_ENVIRONMENT is set in the manifest; the correct
GwUrl is read from appsettings.Staging.json or appsettings.Production.json
depending on the environment — as intended.

Co-authored-by: Cursor <cursoragent@cursor.com>

k8s/staging/frontoffice-deployment.yaml

@@ -28,10 +28,6 @@ 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"