fix(webhook): get currency from channel.currency_code instead of top-level

Saleor webhook payload stores currency in channel.currency_code,
not as a top-level currency field. Updated interfaces and conversion
function to use the correct location.

src/app/api/webhooks/saleor/route.ts

@@ -48,7 +48,10 @@ interface SaleorOrderPayload {
   lines: SaleorLineItemPayload[];
   total_gross_amount: string;
   shipping_price_gross_amount?: string;
-  currency: string;
+  channel: {
+    currency_code: string;
+  };
+  currency?: string; // Fallback for line items
   language_code?: string;
   metadata?: Record<string, string>;
 }
@@ -160,20 +163,20 @@ function convertPayloadToOrder(payload: SaleorOrderPayload): SaleorOrder {
       totalPrice: {
         gross: {
           amount: parseInt(line.total_price_gross_amount),
-          currency: line.currency,
+          currency: line.currency || payload.channel.currency_code,
         },
       },
     })),
     total: {
       gross: {
         amount: parseInt(payload.total_gross_amount),
-        currency: payload.currency,
+        currency: payload.channel.currency_code,
       },
     },
     shippingPrice: payload.shipping_price_gross_amount ? {
       gross: {
         amount: parseInt(payload.shipping_price_gross_amount),
-        currency: payload.currency,
+        currency: payload.channel.currency_code,
       },
     } : undefined,
     languageCode: payload.language_code?.toUpperCase(),