Add hosting deployment setup and backend health endpoint

HOSTING_DEPLOY.md

@@ -0,0 +1,33 @@
+# Hosting Deployment
+
+## 1) Prerequisites
+- Docker Engine + Docker Compose plugin
+- Domain pointing to your host IP
+- (Optional) HTTPS reverse proxy in front of port 80
+
+## 2) Prepare environment
+```bash
+cp backend/.env.example backend/.env
+cp deploy/.env.hosting.example deploy/.env
+```
+
+Edit `backend/.env`:
+- `SECRET_KEY`
+- `BASE_URL` and `FRONTEND_URL` (your real domain)
+- `SSO_ENABLED=true` + `ZITADEL_*` only if you use SSO
+
+## 3) Pull and run published images
+```bash
+docker compose --env-file deploy/.env -f deploy/docker-compose.hosting.yml pull
+docker compose --env-file deploy/.env -f deploy/docker-compose.hosting.yml up -d
+```
+
+## 4) Verify
+- Frontend: `http://<your-host>/`
+- Backend health: `docker compose -f deploy/docker-compose.hosting.yml logs backend`
+- Frontend health: `docker compose -f deploy/docker-compose.hosting.yml logs frontend`
+
+## Notes
+- Frontend uses same-origin `/api` in production, so no hardcoded API host is required.
+- Backend health endpoint is `/health`.
+- If you need local frontend->local backend development, use `frontend/.env.local`.