Schedule account deletion

Schedule the deletion of the account — ONE step, no confirmation session (the POST /me/account/delete flow that used to precede this call is gone: it was a code on another channel followed by the same code again). The signed-in owner needs a consumed single-use account_delete step-up grant whose one target is the account's own id (403 2fa_required; reason: target_mismatch when the grant names other ids); an API key answers 403 owner_session_required. Right now: the account is locked for a 7-day grace period — every session route but the lock page's own, the 2FA family and the session plumbing answers 403 account_scheduled_for_deletion (with scheduled_for), every API key answers the same on every route, you are signed out everywhere, the account's OWN proofs, delegations and consent authorizations are suspended (verifiers and gated servers see it within about a minute), its public pages and badges go dark, and new requests addressed to it and identity checks through its circles are declined. Proofs of decisions already made, and proofs issued to others, stay valid. On the date: billing is settled first (an unpaid final invoice puts the deletion on_hold with a Pay-invoice link rather than deleting past it), then everything owned is deleted and the account's own standing credentials are revoked for good. Cancel any time before that with POST /me/account/deletion/cancel (a code) or the emailed link; cancelling restores what was paused. A repeat call while scheduled answers 200 with already_scheduled: true and the existing date.