REFACTOR(app): migrate to vault secrets

- Migrate from SealedSecret to Vault
- Use ExternalSecrets operator

deploy/k8s/overlays/dev/kustomization.yaml

@@ -7,7 +7,7 @@ resources:
   - ../../base
   - resourcequota.yaml
   - namespace.yaml
-  - sealed-todo-secrets.yaml
+  - externalsecret.yaml
 
 commonLabels:
   environment: development
@@ -15,7 +15,7 @@ commonLabels:
 # 이미지 태그 설정
 images:
   - name: ghcr.io/mayne0213/todo
-    newTag: develop-sha-489b5be29a98d8ca1fc8b92aba3f0981806cdc8c
+    newTag: develop-sha-741395c60d615ff33f6d36e712090cd9eebb2f01
 
 patchesStrategicMerge:
   - deployment-patch.yaml