🧹 Dockerize and automate SQLite backups

[fusion94]

Summary

Today the deployment story (deployment.md) is "manually git pull + npm install + systemd restart, copy the SQLite file by hand for backups." That's brittle. Containerize the stack and run automated backups.

Proposed Approach

Containers

• Dockerfile for frontend (multi-stage Vite build + nginx serving the dist).
• Dockerfile for backend (node:20-alpine, copy server/, install, run node index.js).
• docker-compose.yml wiring both, plus a named volume for server/data/users.db and server/uploads/.
• Nginx in the frontend image proxies /api and /uploads to the backend container.

Backups

• A small sidecar container (or cron job in the backend) running sqlite3 users.db ".backup /backups/users-$(date +%F-%H%M).db" every N hours.
• Optional: upload to S3/B2 with rclone (env-configurable bucket/credentials).
• Keep N most recent local copies; older ones rotated.

Docs

• Update deployment.md to point at docker compose up -d as the primary path.
• Document backup retention and restore procedure.

Acceptance Criteria

• docker compose up runs the full stack locally.
• DB and uploads survive container restarts via volumes.
• Backup files appear in the configured directory on the documented schedule.
• Restore-from-backup procedure documented in deployment.md.