feat(loyalty): pay own orders with EnakPoint from the app

Adds POST /customer/orders/:id/pay-with-points (docs/prd-point-coin.md F9,
PC-306) for the customer app and self-order. It uses the same payment path
as the cashier, approved by the customer's PIN instead of a code: the
session alone is not enough (K8), and a wrong PIN takes nothing and counts
toward the lock.

A customer can pay only their own order; any other order, and one that
does not exist, answer 404 alike, so the endpoint does not reveal other
customers' orders. The method is the organization's EnakPoint method, no
cashier is recorded, and settling the order triggers earning through the
same onOrderPaid hook as every other payment.

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

internal/processor/point_payment_processor.go

@@ -319,3 +319,18 @@ func formatRupiah(n int64) string {
 	}
 	return string(out)
 }
+
+// PointMethodID returns the organization's EnakPoint payment method.
+func (p *PointPaymentProcessor) PointMethodID(ctx context.Context, organizationID uuid.UUID) (uuid.UUID, error) {
+	return p.repo.PointMethodID(ctx, organizationID)
+}
+
+// OrderOwner returns the organization and customer of an order, for checking that a
+// customer pays only their own order.
+func (p *PointPaymentProcessor) OrderOwner(ctx context.Context, orderID uuid.UUID) (organizationID uuid.UUID, customerID *uuid.UUID, err error) {
+	order, err := p.repo.GetOrder(ctx, orderID, false)
+	if err != nil {
+		return uuid.Nil, nil, err
+	}
+	return order.OrganizationID, order.CustomerID, nil
+}