Issue a one-time bootstrap token for a bring-your-own server

Generates a single-use token (~10 min TTL) plus the curl-pipe one-liner that installs the agent on a Linux host you own. The agent self-registers on first contact and joins your fleet. The first external server is free on every account: Starter (no Impreza service) allows 1, Bundled (any active Impreza VPS) 5, and the Unlimited plan has no limit. used counts registered external servers plus install tokens not yet used, this one included. New external servers are also limited per day (429). The token is returned once; only its hash is stored.