On checkout error, customer can click "send us your order details" instead of opening their email app. Posts to /api/invoice-request which: - Emails shop@ with full order details, reply-to set to customer's address so replies go directly to them - Sends customer a confirmation email with order summary Falls back to the mailto link if the API call fails. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>