REFACTOR(repo): to independent app management

- pattern
- monitoring/kustomization.yaml now only manages application.yaml (App
  of Apps)
- Each app independently manages its own ArgoCD Application via
  kustomization.yaml
- Apps are fully self-contained: argocd.yaml, namespace.yaml, and app-
  specific resources
- Cleaner separation: no central app list to maintain

prometheus/kustomization.yaml

@@ -2,7 +2,6 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 
 resources:
-  # ArgoCD Application은 monitoring/kustomization.yaml에서 관리
-  # - argocd.yaml
+  - argocd.yaml
   - namespace.yaml
   - vault/postgresql-password.yaml