feat(k8s): publish the portals through the labs Caddy (refs #177)

Adds a `keycloakUrl` chart value: when set, it replaces host + Keycloak's
NodePort as the pinned issuer and the portals' OIDC authority, so the stack
works behind the existing *.labs.respellion.tech Caddy over HTTPS. Empty keeps
today's behaviour. The deploy workflow passes the KEYCLOAK_URL repo variable.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

infra/docker-compose.yml

@@ -57,9 +57,6 @@ services:
       # share this anchor and ignore it — they don't run uwsgi.
       UWSGI_PROCESSES: "1"
       UWSGI_THREADS: "2"
-      # Same lever for oz-celery: unset, the worker forks one process per CPU (22 on the lab node,
-      # ~225 MB each), which OOM-killed the shared runner mid-verify-stack. Only celery reads it.
-      CELERY_WORKER_CONCURRENCY: "2"
       DJANGO_SETTINGS_MODULE: openzaak.conf.docker
       SECRET_KEY: ${OZ_SECRET_KEY:-dev-only-not-for-production}
       DB_HOST: oz-db
@@ -147,8 +144,6 @@ services:
       # 1 uWSGI worker, not the image default of 4×4 (#147) — see the oz-env note above.
       UWSGI_PROCESSES: "1"
       UWSGI_THREADS: "2"
-      # Two celery workers, not one per CPU — see the oz-env note above.
-      CELERY_WORKER_CONCURRENCY: "2"
       DJANGO_SETTINGS_MODULE: nrc.conf.docker
       SECRET_KEY: ${NRC_SECRET_KEY:-dev-only-not-for-production}
       DB_HOST: nrc-db

infra/helm/big-reference/values.yaml

@@ -76,7 +76,6 @@ envGroups:
   oz:
     UWSGI_PROCESSES: "1"
     UWSGI_THREADS: "2"
-    CELERY_WORKER_CONCURRENCY: "2"
     DJANGO_SETTINGS_MODULE: openzaak.conf.docker
     SECRET_KEY: dev-only-not-for-production
     DB_HOST: oz-db
@@ -99,7 +98,6 @@ envGroups:
   nrc:
     UWSGI_PROCESSES: "1"
     UWSGI_THREADS: "2"
-    CELERY_WORKER_CONCURRENCY: "2"
     DJANGO_SETTINGS_MODULE: nrc.conf.docker
     SECRET_KEY: dev-only-not-for-production
     DB_HOST: nrc-db