fix: support multiple copies printing natively in backend print service

inventory-web/src/views/stock/inbound/buy.vue

@@ -1252,6 +1252,14 @@ watch(() => [form.in_quantity, form.unit_price], () => {
   }
 })
 
+// 联动优化：当入库数量变化时，自动同步打印份数（除非用户已手动修改过）
+watch(() => form.in_quantity, (newQty) => {
+  if (dialogStatus.value === 'create' && newQty && newQty > 0) {
+    // 仅在创建模式下自动同步
+    form.print_copies = newQty
+  }
+})
+
 const fetchData = async () => {
   loading.value = true
   try {