fix: serve a leaf certificate, not the CA

LibreChat served the lab CA's own certificate as its server certificate — a
CA:TRUE certificate valid for the whole *.sttlab.local wildcard, from a
hand-made tls.yaml that also carried the CA's private key. Gitignored, so never
leaked, but the only service in the estate still copying the CA around instead
of being issued a leaf.

Now a cert-manager Certificate for librechat.sttlab.local: CA:FALSE, one
dnsNames, key generated in the cluster and rotated there.

The two uses of that Secret had to be separated first, which is the part worth
knowing: sttlab-tls was both the ingress certificate and the CA bundle mounted
as NODE_EXTRA_CA_CERTS for outbound calls. Replacing it with a leaf alone would
have left LibreChat unable to verify Keycloak. The CA certificate now comes from
ca-configmap.yaml — the certificate, never the key, committed like the agents'.

Verified: the ingress serves CA:FALSE with SAN librechat.sttlab.local, the pod's
outbound call to Keycloak returns 200 with TLS verified, and the old secret is
deleted.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

k8s/kustomization.yaml

@@ -5,6 +5,7 @@ resources:
   - namespace.yaml
   - secret.yaml
   - configmap.yaml
+  - ca-configmap.yaml
   - mongodb/pvc.yaml
   - mongodb/statefulset.yaml
   - mongodb/service.yaml
@@ -14,5 +15,5 @@ resources:
   - librechat/configmap-app.yaml
   - librechat/deployment.yaml
   - librechat/service.yaml
-  - ingress/tls.yaml
+  - ingress/certificate.yaml
   - ingress/ingress.yaml