1.1.0

feat: pay a vendor payout row through a payment request (1.1.0)

• New payment request purpose "Vendor payout (marketplace)" linked to an unpaid
  payout row of a period (root store only, same currency, not above the row).
• The payout screen gets "Pay through a payment request"; once the request is
  fully paid out the row is marked paid with the transaction reference and the
  vendor is notified. Preparing and paying keep separate permissions.
• The purpose is offered only while the shop's payment requests are set up.
• requireCore 3.1; README updated.

Co-Authored-By: Claude Opus 5.5 noreply@anthropic.com