REFACTOR(secrets): flatten Vault paths

- Change secret paths from <category>/<app> to <app>
- databases/postgresql → postgresql
- databases/minio → minio
- databases/pgweb → pgweb
- cluster-infrastructure/velero → velero

postgresql-dev/manifests/secret.yaml

@@ -14,9 +14,9 @@ spec:
   data:
     - secretKey: password
       remoteRef:
-        key: databases/postgresql-dev
+        key: postgresql-dev
         property: PASSWORD
     - secretKey: postgres-password
       remoteRef:
-        key: databases/postgresql-dev
+        key: postgresql-dev
         property: POSTGRES_PASSWORD