PIN verify -> request.session.authenticate(type=fp_tablet_pin) -> new
session sid, cookie swap, audit event written. Failed attempts also
written to audit log (failed_unlock, failure_reason=wrong_pin or
locked_out or no_pin_set or user_inactive).
OLD /fp/tablet/unlock stays alive during the 1-week overlap window
per spec Section 5.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
086ff512b6