feat: 借库归还日期贯穿申请/审批/扫码借库；BOM 套餐添加与打印、缺货写入申请原因

inventory-web/src/views/transaction/borrow.vue

@@ -416,11 +416,25 @@ const loadApprovalRequests = async () => {
   }
 }
 
-// ★ 切换审批单时：清空购物车和签名，防止跨单据污染
+// ★ 切换审批单时：带出申请时填写的归还日期/长期借用，并清空购物车和签名，防止跨单据污染
 const handleApprovalChange = (val: number | null) => {
   if (!val) {
     selectedApprovalId.value = null
   }
+  // 从申请单明细快照中带出"预计归还日期"（申请时通过 items_json 存储，无需改数据库）
+  const req = approvalRequests.value.find(r => r.id === val)
+  const firstItem = req?.items?.[0]
+  if (firstItem?.is_indefinite) {
+    isIndefinite.value = true
+    form.expected_return_time = ''
+  } else if (firstItem?.expected_return_time) {
+    isIndefinite.value = false
+    form.expected_return_time = firstItem.expected_return_time
+  } else {
+    // 旧申请单/未填时间：保持手动选择
+    isIndefinite.value = false
+    form.expected_return_time = ''
+  }
   cartItems.value = []
   signatureFile.value = null
   signaturePreviewUrl.value = ''