Fix Kaniko registry auth and push target for Harbor builds.

Mount docker config as config.json (Kaniko requirement), push via
harbor-registry internal URL, and wire harbor_registry_user credentials
in Helm/GitOps values.

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

gitops/platform/values-abrban.example.yaml

@@ -11,6 +11,11 @@
 namespace: cloudhost
 createNamespace: false
 
+registry:
+  credentialsSecret: harbor-core
+  credentialsPasswordKey: REGISTRY_CREDENTIAL_PASSWORD
+  username: harbor_registry_user
+
 global:
   storageClass: local-path