Stable checkpoint — Keycloak host port 9090 → 8888

Cumulative since stable-v1.2.4 :
- Keycloak Docker host port migrated from 9090 to 8888 to avoid conflict
  with the elgato-mcp-server global host process on dev macOS machines
- 8090 was considered but already documented as kind ingress port in this repo
- Updates : docker-compose.yml, bin/run/status.sh, CLAUDE.md, infra/keycloak/README.md

Post-merge main pipeline #2480704203 green at 18:20.