FIX(app): use POSTGRES_PASSWORD from Vault

- Change PASSWORD to POSTGRES_PASSWORD
- Use correct Vault key name

deploy/k8s/overlays/prod/externalsecret.yaml

@@ -54,5 +54,5 @@ spec:
     - secretKey: password
       remoteRef:
         key: databases/postgresql
-        property: PASSWORD
+        property: POSTGRES_PASSWORD
 

deploy/k8s/overlays/prod/kustomization.yaml

@@ -15,5 +15,5 @@ commonLabels:
 # 이미지 태그 설정 (ArgoCD Image Updater가 자동으로 업데이트)
 images:
   - name: gitea0213.kro.kr/bluemayne/mas
-    newTag: main-sha-956fbba3b771b37eb782f5722f675374f507cd7c
+    newTag: main-sha-c2478e77782ada7a8bc51de2f4f0ef4530dd67b2