Dockerize the stack; release camera hardware on toggle off

[Shinchan493]

Add full containerization and fix a camera-privacy issue, rebased onto the latest main (the resizable code/whiteboard split already landed upstream, so that local change was dropped in favor of the upstream one).

Docker:

• server/Dockerfile (multi-stage: build TS -> run compiled dist)
• client/Dockerfile + nginx.conf (CRA build served by nginx)
• docker-compose.yml (db + server + client, one command)
• .dockerignore for both; .env.example templates
• db.config: DB_SSL=false disables SSL for the local plaintext Postgres container while managed hosts (Render/Neon) keep SSL by default

Camera privacy:

• toggling the camera off now STOPS the video track (releases the hardware/indicator light) and removes it from peers, instead of only disabling frames; turning it on re-acquires and re-shares the track. Sessions also join with the camera fully released, not just muted.

Windows dev + tooling:

• cross-env + ts-node/register so npm run serve works on Windows
• .gitignore: keep .env.example, ignore node_modules/coverage/logs
• README: Docker Compose quickstart + Docker deployment notes