Create a Fly Machine via the Machines REST API

Documented steps

1. Get a Fly API token: `fly auth token` (or `fly tokens create` for an org-restricted/auto-expiring token). Use API host https://api.machines.dev for calls outside the private WireGuard network.
2. Ensure the app exists (create with POST /v1/apps with {"app_name":...,"org_slug":...}).
3. Create a Machine with `curl -X POST -H "Authorization: Bearer $FLY_API_TOKEN" -H "Content-Type: application/json" https://api.machines.dev/v1/apps/<app>/machines` and a body with the image, a `config.init.exec` command, `config.guest` (cpu_kind/cpus/memory_mb), and optionally a `restart.policy`.
4. The POST returns a Machine object with its `id`, `name`, `state`, `region`, and `private_ip`.
5. Machine starts automatically after creation unless `skip_launch:true` is set.
6. Manage it further: POST /v1/apps/<app>/machines/<id>/stop, /start, /restart, /cordon, /uncordon; GET /.../wait to block until a target state; DELETE to destroy.
7. Official docs: https://fly.io/docs/machines/api/ (machines-resource) — OpenAPI at https://docs.machines.dev/