Relay HTTP API

Base URL: https://relay.fau.run JSON bodies; errors are {"error":"…","detail":"…"}.

`GET /v1/health`

{ "status": "ok", "nodes_connected": 12, "version": "…" }

Static JSON: what the relay can observe (can_see / cannot_see), retention notes, and metrics names. Metadata only — no mail.

Method	Path
`POST`	`/v1/queue/{hostname}` — body `{envelope, request_id?}` → `202`
`GET`	`/v1/queue/reply/{request_id}` — `200` / `204` / `404`

Node self-service only:

fau/1. Breaking changes bump the version. This site plus repo docs/protocol.md are the contract.