WebAuthn platform passkeys: opt-in enrollment after a password login, a
password-less sign-in that mints the same 14-day campaign-token, and
revocation from the profile. The session is minted through Payload's public
pieces (checkLoginPermission, addSessionToUser, getFieldsToSign, jwtSign)
inside a transaction with an advisory lock, so a passkey login neither
bypasses a lockout nor evicts the account's other sessions. The rpID is
derived from NEXT_PUBLIC_SITE_URL and resolves to null when the request host
disagrees, so previews never offer a ceremony the browser would refuse.
