Build local release artifacts and prepare Compose deployment [skip ci]

docs/deployment.md

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+# Docker Compose deployment
+
+This deployment builds the panel and web UI from the checked-out source. It does
+not need GitHub Actions or a published GHCR image.
+
+1. Install Docker Engine with the Compose plugin on a Linux host. Point a DNS
+   name at that host and arrange HTTPS through your reverse proxy.
+2. Check out the commit you want to deploy, then copy `.env.example` to `.env`.
+   Set `ADMIN_PASSWORD` to a unique password and `PUBLIC_URL` to the public
+   `https://` URL. Set `SCOPENET_TRUSTED_PROXIES` only to the IP addresses of
+   proxies that send forwarding headers.
+3. Run:
+
+   ```bash
+   docker compose config --quiet
+   docker compose up -d --build
+   docker compose ps
+   docker compose logs --tail=100 panel
+   ```
+
+The panel listens on `PANEL_PORT` (default `8080`). Docker checks
+`/scopenet-panel healthcheck` inside the container. Wait for `healthy` in
+`docker compose ps` before directing players to it. If `ADMIN_PASSWORD` is
+blank on first start, the generated password appears in the panel logs.
+
+The named `panel-data` volume holds the database, uploads, hosted launcher
+downloads, and the generated JWT signing key. Preserve that volume when
+upgrading. To back it up, stop the panel, archive the volume with a temporary
+container, then start it again:
+
+```bash
+docker compose stop panel
+docker run --rm -v scopenet-mc_panel-data:/data:ro -v "$PWD":/backup alpine tar czf /backup/panel-data.tar.gz -C /data .
+docker compose up -d
+```
+
+If your Compose project has a different name, use the volume name shown by
+`docker volume ls`. To upgrade, pull the desired commit and run
+`docker compose up -d --build` again. Do not use `docker compose down -v` unless
+you intend to delete the panel data.