Reframe the deployment docs around the actual product story: Fabro
runs as a server, and the only deployment question is where that
server runs (laptop vs self-hosted Docker). Drop the Render, Fly.io,
and DigitalOcean guides and their config files; keep Railway as the
managed shortcut.
- New: administration/deployment.mdx (overview, two-mode framing)
- New: administration/self-host-docker.mdx (compose-first how-to)
- Move: administration/deploy-server.mdx -> reference/server-operations.mdx
(it was operational reference, not deploy guidance)
- Delete: deploy-render.mdx, deploy-fly-io.mdx, deploy-digital-ocean.mdx
- Delete: render.yaml, fly.toml, railway.toml, Dockerfile.deploy
- docker-compose.yaml: load .env if present so users can drive the
stack from a single env file end-to-end
- Update internal links and the docs-test that pinned the old path
