"Let anyone who schedules with you see this": promote a host-scoped save, confirmed by email

After a save that went live only for the host whose ask-link k it carried, queue the same payload as a normal pending save (the same limits as POST /api/manual-availability; the issuer is noted, and its confirmation email and Confirm page say that host already sees the times). The confirmation click publishes it for everyone. k must be a valid host-issued signature for this email. Anonymous callers need a Turnstile token and may not use an address that has a connected account.