In-cluster clients resolving a platform hostname over its PUBLIC name got the
off-cluster answer, so pod->keycloak.home.keithjackson.dev hit a path that does not
serve the *.home.keithjackson.dev SNI -> `tls: unrecognized name` (oauth2-proxy OIDC
discovery crash; Grafana generic_oauth would hit the same wall).
Add a GitOps-managed coredns-custom ConfigMap (kube-system) that k3s CoreDNS imports as
a `*.server` block. The template plugin answers the whole home.keithjackson.dev zone with
${GATEWAY_VIP} (the shared Gateway VIP), so pod->public-hostname traffic hairpins through
the Gateway with the correct SNI -> wildcard cert validates. CoreDNS reloads the ConfigMap
live (no pod restart). Wired into platform/kustomization.yaml (Phase 2 network core).
Co-Authored-By: Claude Opus 4.8 <[email protected]>
