[bojemoi] feat(monitoring): swarm-exporter service + métriques Prometheus sur le registry

Commit `cee9b15`

stack/02: ajout service swarm-exporter (port 9324, manager only, réseau monitoring)
volumes/monitoring/swarm-exporter.py: script exporter métriques Docker Swarm
registry/config.yml: activation debug endpoint :5001 + /metrics Prometheus

Co-Authored-By: Claude Sonnet 4.6 (1M context) noreply@anthropic.com