Architecture (tree view)
- back/ (NestJS)
- src/
- Dockerfile
- docker-compose.yml (service definition)
- front/ (Astro + React)
- src/components/
- Dockerfile
- docs/ (Docusaurus)
- docker-compose.yml (root orchestrates back, front, docs)
- .env.example
Runtime: frontend connects to backend via Socket.IO; backend routes messages to session rooms.