fix: restrict order quantity edits to pending orders

apps/api/src/orders/order-status.ts

@@ -1,7 +1,7 @@
 import type { OrderStatus } from "@orderops/shared/order-status";
 
 export function canEditOrderItems(status: OrderStatus) {
-  return status === "pending" || status === "processing";
+  return status === "pending";
 }
 
 export function canEditShippingAddress(status: OrderStatus) {