fix(infra): bake config into images so compose-smoke passes on CI (refs #30)

Root cause of the compose-smoke failure (found in the runner logs):

  oz-init-1 | CommandError: Yaml file
              `/app/setup_configuration/data.yaml` does not exist.

The ubuntu-latest runner runs the job inside a container, so
`docker compose up` starts the stack as SIBLING containers via the host
daemon. A relative bind mount (./openzaak/setup_configuration) resolves to
a path inside the job container that the daemon can't see, so Docker mounts
an empty dir and the init container can't find data.yaml. The same trap hit
nrc-init (data.yaml), flowable-init (the BPMN) and keycloak (realm import).

Fix: bake the assets into small derived images instead of bind-mounting:
  - infra/openzaak/Dockerfile        -> register-referentie/openzaak:dev
  - infra/opennotificaties/Dockerfile-> register-referentie/opennotificaties:dev
  - infra/keycloak/Dockerfile        -> register-referentie/keycloak:dev
  - flowable-init: build.dockerfile_inline bakes workflows/registratie.bpmn

Base versions stay build args (OPENZAAK_TAG / OPENNOTIFICATIES_TAG), so the
pinning is unchanged. Applied to both the consolidated compose and the
per-service composes, so local Podman and CI use one mechanism — no bind
mounts, no SELinux `:z`, no world-readable requirement.

Verified locally: `podman build` of the OpenZaak and BPMN images produces
the file at the expected in-container path.

Docs: docs/runbooks/gitea-actions-gotchas.md explains the DinD bind-mount
trap and the bake fix; openzaak.md and ci.md point at it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

infra/keycloak/docker-compose.yml

@@ -9,7 +9,10 @@
 # Admin console: http://localhost:8180/  (admin / admin — dev only)
 services:
   keycloak:
-    image: quay.io/keycloak/keycloak:26.1
+    build:
+      context: .
+      dockerfile: Dockerfile
+    image: register-referentie/keycloak:dev
     command: ["start-dev", "--import-realm"]
     environment:
       KC_BOOTSTRAP_ADMIN_USERNAME: admin
@@ -21,8 +24,6 @@ services:
       KC_HTTP_ENABLED: "true"
     ports:
       - "8180:8080"
-    volumes:
-      - ./realms:/opt/keycloak/data/import:ro,z
     networks: [cg]
 
 networks: