feat(keycloak): Gateway-API as an alternative to the two Ingresses

Group 3 of the #114 sweep, first chart. keycloak has TWO Ingress objects -
the public hostname and the admin hostname - so it gets TWO HTTPRoutes, with
httpRoute.admin.parentRefs falling back to httpRoute.parentRefs exactly as
ingress.admin.className falls back to ingress.className: "which data path" is
a property of the Gateway in this API, not of the route, so an internal
Gateway here is what an internal ingress class is in the other mode.

The admin route stays gated on ingress.admin.enabled, because that value is
not an Ingress switch - it also decides whether KC_HOSTNAME_ADMIN is set on
the Deployment, i.e. whether the admin hostname exists at all. Switching to
Gateway mode therefore must not require turning it off.

FIXED ALONG THE WAY: the admin Ingress did not hang off ingress.enabled.
Measured on origin/main, `helm template -f ci/keycloak/test-values.yaml --set
ingress.enabled=false` emitted kc-keycloak-admin-ingress - so
"ingress.enabled: false" did not mean "no Ingress", and ingress.clusterIssuer
stayed required for an object nobody asked for. It also made Gateway mode
impossible: the admin Ingress would have gone on claiming the admin host next
to the admin HTTPRoute, one host over two data paths, which is the exact
conflict the mutual exclusion exists to prevent. The default render is
unchanged; what changed is a combination that could not be coherent.

WHAT THIS MODE DROPS, MEASURED ON THE LIVE CLUSTER rather than inferred. On
2026-10-12 BOTH of this chart's Ingress objects in jk-cluster carried

    nginx.ingress.kubernetes.io/proxy-buffer-size:    16k
    nginx.ingress.kubernetes.io/proxy-buffers-number: 4

set by the OPERATOR through ingress.annotations and ingress.admin.annotations
- the chart sets neither, which is why reading the chart alone does not reveal
them. The Gateway API has no annotation channel and no counterpart for proxy
buffer sizing; it is implementation policy, not routing. Per decision 1 of
#114 the chart renders no policy object, so this is NAMED and not rebuilt, in
values.yaml, in the schema and in the Gateway branch of NOTES.txt, with the
consequence spelled out in Keycloak's own terms: large headers (JWTs, SAML
assertions, long Set-Cookie chains on the login flow) make a too-small buffer
answer 502 at the PROXY while Keycloak logs the request as successful.

Named and deliberately not touched: four further Ingress objects in the same
namespace (keycloak-realm-*-ingress, with app-root) belong to the Helm release
jk-cluster-config-fleet-cd-keycloak-realm-ingress, i.e. to another repository.
They point at this release's Service under four further hostnames. This chart
renders exactly the two routes its own two Ingresses cover.

Minor: additive, defaults unchanged. Empty helm template diff against
origin/main with ci/keycloak/test-values.yaml.

Part of #114

keycloak/templates/keycloak.ingress.yaml

@@ -29,6 +29,21 @@ time outside this template - as KC_HOSTNAME on the Deployment - so it stays
 required even with ingress.enabled: false, and its required() lives in the
 keycloak.frontendUrl helper rather than here. clusterIssuer is read only in
 this file, so switching both Ingresses off frees it.
+
+BOTH OBJECTS HANG OFF ingress.enabled, AND THE ADMIN ONE DID NOT USED TO
+(fixed with the Gateway-API support, Gitea #114). ingress.admin.enabled is NOT
+an Ingress switch: it decides whether KC_HOSTNAME_ADMIN is set on the
+Deployment, i.e. whether the admin hostname is in play at all - so the admin
+Ingress used to render with ingress.enabled: false, which meant
+"ingress.enabled: false" did not mean "no Ingress" and clusterIssuer was still
+required for an object nobody asked for. Measured before the fix:
+`helm template -f ci/keycloak/test-values.yaml --set ingress.enabled=false`
+emitted kc-keycloak-admin-ingress and nothing else of the routing path. It also
+made Gateway mode impossible: switching httpRoute on leaves ingress.enabled
+false, and the admin Ingress would have gone on claiming the admin host next to
+the admin HTTPRoute - one host, two data paths, the exact conflict the mutual
+exclusion exists to prevent. The default render is unchanged (ingress.enabled
+defaults to true); what changed is a combination that could not be coherent.
 */ -}}
 {{- $adminEnabled := eq (include "keycloak.adminHostnameEnabled" .) "true" }}
 {{- if .Values.ingress.enabled }}
@@ -61,10 +76,8 @@ spec:
         - {{ required "A Domain/Host must be provided (ingress.domain)" .Values.ingress.domain }}
       secretName: tls-{{ .Release.Name }}-{{ .Chart.Name }}-ingress
 {{- end }}
-{{- if $adminEnabled }}
-{{- if .Values.ingress.enabled }}
+{{- if and .Values.ingress.enabled $adminEnabled }}
 ---
-{{- end }}
 apiVersion: networking.k8s.io/v1
 kind: Ingress
 metadata: