fix(gateways): add explicit group: "" to all certificateRefs entries

The Gateway API admission server defaults certificateRefs[].group to ""
when it is omitted. ArgoCD diffed the desired state (no group field) against
the live state (group: "") and flagged every gateway as out of sync.

Fix: explicitly set group: "" in all certificateRefs entries so the
rendered manifest matches the API server's canonical form exactly.

Affected: artifactapi, cattle-system, consul, litellm, paperclip,
puppet (puppetboard + puppetdb), vault.

apps/base/vault/gateway.yaml

@@ -35,7 +35,8 @@ spec:
       tls:
         mode: Terminate
         certificateRefs:
-          - kind: Secret
+          - group: ""
+            kind: Secret
             name: vault-tls
     - name: vault-direct
       port: 8200
@@ -46,5 +47,6 @@ spec:
       tls:
         mode: Terminate
         certificateRefs:
-          - kind: Secret
+          - group: ""
+            kind: Secret
             name: vault-tls