chore: initial project setup with backend, frontend, and infrastructure

Add complete NexaPantry application structure including:
- Docker Compose configuration with PostgreSQL, Redis, FastAPI backend, worker, frontend and Caddy
- Environment configuration template with database, auth, and service settings
- GitHub Actions CI workflow for backend/frontend linting, testing, auditing and Docker builds
- AGPL-3.0 license and comprehensive README with setup, development, and security documentation
- Backend

docs/deployment.md

@@ -0,0 +1,13 @@
+# Deployment
+
+1. Point a domain at the host.
+2. Copy `.env.example` to `.env`.
+3. Replace all secrets and database passwords.
+4. Set `INSTANCE_URL=https://your.domain`.
+5. Set `FRONTEND_ORIGIN=https://your.domain`.
+6. Set `COOKIE_SECURE=true`.
+7. Configure Caddy with your domain instead of `:80` when using automatic TLS.
+8. Start with `docker compose up -d`.
+
+For production, expose only Caddy ports. PostgreSQL, Redis, backend and frontend remain on the private Compose network.
+