feat(swarm): add coordinator service and reorganize compose files

- Add coordinator service to docker-compose.swarm.portainer.yml and
  docker-compose.swarm.yml with full environment config and healthcheck
- Add ANTHROPIC_API_KEY and coordinator settings to .env.swarm.example
- Move docker-compose.override.yml.example and docker-compose.prod.yml
  into docker/ directory
- Add *.bak to .gitignore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -35,6 +35,7 @@ Thumbs.db
 .env.test.local
 .env.production.local
 .env.bak.*
+*.bak
 
 # Credentials (never commit)
 .admin-credentials