REFACTOR(goldilocks): use managedNamespaceMetadata for namespace labels

- Remove namespace.yaml files
- Add managedNamespaceMetadata with Goldilocks label
- Set CreateNamespace=true in syncOptions
- Update kustomization.yaml to remove namespace.yaml references

postgresql-dev/kustomization.yaml

@@ -1,8 +1,4 @@
 apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
-
 resources:
-  # argocd.yaml은 수동으로 관리 (순환 참조 방지)
-  # - argocd.yaml
-  - namespace.yaml
-  - vault/postgresql-password-dev.yaml
+- vault/postgresql-password-dev.yaml