Schedule a signed wake ($0.01)

Registers a wake ?in=<seconds> (30 to 2592000) from now. With ?url=<public https callback>, an Ed25519-signed receipt binding wake_id, scheduled_at and the actual fired_at is POSTed to it at the appointed time, retrying at 30s, 2m, 10m and 30m; the receipt is signed once and retries resend the identical copy — verify against https://soren.com/oracle-key.json. Without url, the wake is a pure timer: poll GET /v1/wake/{id} for free. Callback URLs must consent by echoing a registration challenge (200 with the challenge anywhere in the body) before anything is charged; https only, private address space refused, 50 registrations per target host per day. Nothing is charged until the wake is scheduled. No payload is stored — a wake knows its URL and its time, nothing else. Status and receipt remain readable for 7 days after firing, then the wake is deleted.