real middleman: BTCPay payment gate + webhook + Printful adapter + checkout redirect

frontend/src/pages/Checkout.tsx

@@ -80,12 +80,17 @@ export default function Checkout() {
     setPlacing(true);
     setError(null);
     try {
-      const created = await api.post<Order>('/orders', {
+      const created = await api.post<any>('/orders', {
         customer_email: email,
         items: lines.map((l) => ({ product_id: l.product.id, qty: l.qty })),
       });
       clear();
-      setOrder(created);
+      // redirect straight to the BTCPay payment page so the customer actually pays
+      if (created?.checkout_url) {
+        window.location.href = created.checkout_url;
+        return;
+      }
+      setOrder(created.order);
     } catch (err) {
       setError(err instanceof Error ? err.message : 'Failed to place order');
     } finally {