feat: cut api.riotpiao.com over to the Go gateway and retire Kong

Ingress api/api now backs onto api-gateway:8080; the kong Application, its
Helm values, plugins and llm-routes are removed. Gateway image v0.0.0 is in
the Forgejo registry and the pull secret is in the api namespace.

k8s/bootstrap/ingress/ingress.yaml

@@ -300,10 +300,11 @@ spec:
                 port:
                   number: 8080
 ---
-# NOTE: api.riotpiao.com (Kong) is deliberately NOT here. Its namespace `api` is
+# NOTE: api.riotpiao.com is deliberately NOT here. Its namespace `api` is
 # created in wave 7, and this Application syncs in wave 1 — an Ingress into a
 # namespace that doesn't exist yet would fail and mark this whole app
-# SyncFailed. It lives in k8s/apps/api/ingress.yaml, synced with Kong itself.
+# SyncFailed. It lives in k8s/apps/api/ingress.yaml, synced by the api-gw
+# Application.
 apiVersion: networking.k8s.io/v1
 kind: Ingress
 metadata: