REFACTOR(app): use native Python clients

Major changes:
- Kubernetes tools: Replace subprocess kubectl calls with kubernetes-client library
  - Supports in-cluster config for pod execution
  - Fallback to local kubeconfig for development
  - All k8s tools (nodes, pods, deployments, logs, describe) now use Python API

- PostgreSQL tools: Replace kubectl exec psql with direct psycopg2 connection
  - Connect via Kubernetes service DNS
  - Support for environment-based configuration
  - Improved error handling with proper pgcode/pgerror

- Prometheus tools: Replace kubectl exec wget with direct HTTP requests
  - Use requests library to query Prometheus API
  - Connect via Kubernetes service DNS
  - Configurable via PROMETHEUS_URL env var

- Deployment updates: Add explicit PostgreSQL connection env vars
  - POSTGRES_HOST, POSTGRES_PORT, POSTGRES_USER
  - Already had POSTGRES_PASSWORD from secret

Benefits:
- No longer requires kubectl binary in container
- Faster execution (no subprocess overhead)
- Better error handling and type safety
- Works seamlessly in Kubernetes pods with RBAC

deploy/k8s/overlays/prod/kustomization.yaml

@@ -16,5 +16,5 @@ commonLabels:
 # 이미지 태그 설정 (ArgoCD Image Updater가 자동으로 업데이트)
 images:
   - name: gitea0213.kro.kr/bluemayne/mas
-    newTag: main-sha-28c6e6f8b827900a25c03f3e63c874ddedecf535
+    newTag: main-sha-22b0840afde85b864df82a5c9408da8c78e28195