Stream and inspect Railway deployment and build logs with railway logs

Documented steps

1. Target the linked service, then run `railway logs` to stream its latest deployment's runtime logs.
2. Limit output with `railway logs -n 100` (--lines).
3. Inspect the container build phase (Dockerfile/Nixpacks) with `railway logs --build`.
4. Stream DNS query logs for private-networking services with `railway logs --dns`.
5. Select a different environment with `railway logs -e <env>`.
6. For resource/HTTP metrics alongside logs, use `railway metrics`.