refactor(purchase): 批次概念改为基于 request_no 前缀推导，撤销数据库字段

按用户反馈：不需要新增数据库字段，现有 request_no (PUR-20260831-1021-0001)
本身就能推导批次——去掉末尾4位流水号即为批次前缀。

- 撤销 purchase_request.batch_no 字段（模型/数据库）
- 撤销 create 接口的 batch_no 参数与 generate_batch_no
- 批次标识 = request_no 去掉末尾 -XXXX 段
  getBatchKey('PUR-20260831-1021-0001') = 'PUR-20260831-1021'
- 按批次查询/批量审批接口改用 batch_key (request_no LIKE 前缀)
- 前端列表批次号列、整批弹窗、一键审批本批均基于前缀推导
- 零数据库迁移，历史数据立即可用

inventory-web/src/views/purchase/index.vue

@@ -52,11 +52,11 @@
       </el-table-column>
       <el-table-column prop="requester_name" label="申请人" width="100" />
       <el-table-column prop="approver_name" label="审批人" width="100" />
-      <!-- ★ 批次号列：同一批提交的记录共享，可点击查看整批 -->
+      <!-- ★ 批次号列：同一批提交的记录共享（request_no 去掉末尾流水号），可点击查看整批 -->
       <el-table-column label="批次号" width="170">
         <template #default="{ row }">
-          <el-link v-if="row.batch_no" type="primary" :underline="false" @click="openBatchDialog(row.batch_no)">
-            {{ row.batch_no }}
+          <el-link v-if="getBatchKey(row.request_no)" type="primary" :underline="false" @click="openBatchDialog(row.request_no)">
+            {{ getBatchKey(row.request_no) }}
           </el-link>
           <span v-else style="color:#ccc">-</span>
         </template>
@@ -69,7 +69,7 @@
       <el-table-column label="操作" width="240" fixed="right" align="center">
         <template #default="{ row }">
           <el-button type="primary" link size="small" @click="openDetailDialog(row)">详情</el-button>
-          <el-button v-if="row.batch_no" type="info" link size="small" @click="openBatchDialog(row.batch_no)">整批</el-button>
+          <el-button v-if="getBatchKey(row.request_no)" type="info" link size="small" @click="openBatchDialog(row.request_no)">整批</el-button>
           <template v-if="row.status === 0 && canApprove">
             <el-button type="success" link size="small" @click="handleApprove(row)">通过</el-button>
             <el-button type="danger" link size="small" @click="openRejectDialog(row)">驳回</el-button>
@@ -286,7 +286,7 @@
     <el-dialog v-model="batchDialogVisible" title="采购批次详情" width="900px" destroy-on-close :close-on-click-modal="false" :close-on-press-escape="false">
       <div style="margin-bottom: 12px;">
         <span style="font-weight: 600;">批次号:</span>
-        <el-tag style="margin-left: 6px;">{{ currentBatchNo }}</el-tag>
+        <el-tag style="margin-left: 6px;">{{ currentBatchKey }}</el-tag>
         <span style="margin-left: 12px; color: #909399;">共 {{ batchItems.length }} 条采购记录</span>
         <el-button
             v-if="canApprove && batchItems.some(i => i.status === 0)"
@@ -456,25 +456,26 @@ const detail = ref<any>({})
 
 // ★ 整批查看
 const batchDialogVisible = ref(false)
-const currentBatchNo = ref('')
+const currentBatchKey = ref('')
 const batchItems = ref<any[]>([])
 
-// 打开整批查看弹窗
-const openBatchDialog = async (batchNo: string) => {
-  currentBatchNo.value = batchNo
+// 打开整批查看弹窗（传入任一 request_no，推导批次前缀）
+const openBatchDialog = async (requestNo: string) => {
+  const batchKey = getBatchKey(requestNo)
+  currentBatchKey.value = batchKey
   batchItems.value = []
   batchDialogVisible.value = true
   try {
-    const res: any = await getPurchaseByBatch(batchNo)
+    const res: any = await getPurchaseByBatch(batchKey)
     batchItems.value = res.data?.items || []
   } catch (err: any) {
     ElMessage.error(err?.msg || '加载批次记录失败')
   }
 }
 
-// 批量通过本批（按批次号）
+// 批量通过本批（按批次前缀）
 const handleBatchApproveByNo = async () => {
-  if (!currentBatchNo.value) return
+  if (!currentBatchKey.value) return
   const pendingCount = batchItems.value.filter(i => i.status === 0).length
   if (pendingCount === 0) return ElMessage.warning('本批没有待审批记录')
   try {
@@ -487,9 +488,9 @@ const handleBatchApproveByNo = async () => {
 
   batchLoading.value = true
   try {
-    const res: any = await batchApprovePurchase({ batch_no: currentBatchNo.value, action: 'approve' })
+    const res: any = await batchApprovePurchase({ batch_key: currentBatchKey.value, action: 'approve' })
     ElMessage.success(res?.msg || '本批已全部通过')
-    await openBatchDialog(currentBatchNo.value)  // 刷新整批数据
+    await openBatchDialog(batchItems.value[0]?.request_no || currentBatchKey.value)  // 刷新整批数据
     await fetchData()
   } catch (err: any) {
     ElMessage.error(err?.msg || '批量通过失败')
@@ -894,14 +895,12 @@ const syncRemarkToAll = () => {
   ElMessage.success('已将第一行备注同步到所有行')
 }
 
-// ★ 生成采购批次号（与后端 generate_batch_no 格式一致）
-const generateBatchNo = () => {
-  const now = new Date()
-  const pad = (n: number) => String(n).padStart(2, '0')
-  const dateStr = `${now.getFullYear()}${pad(now.getMonth() + 1)}${pad(now.getDate())}`
-  const timeStr = `${pad(now.getHours())}${pad(now.getMinutes())}`
-  const rand = Math.random().toString(16).slice(2, 6).toUpperCase()
-  return `BATCH-${dateStr}-${timeStr}-${rand}`
+// ★ 推导批次前缀：request_no 去掉末尾"-流水号"（如 PUR-20260831-1021-0001 → PUR-20260831-1021）
+const getBatchKey = (requestNo: string): string => {
+  if (!requestNo) return ''
+  // 去掉末尾的 -0001 段（最后5个字符：- + 4位流水）
+  const idx = requestNo.lastIndexOf('-')
+  return idx > 0 ? requestNo.slice(0, idx) : requestNo
 }
 
 // ★ 照片一键同步所有行：取第一行的照片深拷贝到所有行
@@ -952,15 +951,12 @@ const submitForm = async () => {
     }
   }
 
-  // 3. 逐行提交（每行携带公共信息 + 同一批次号）
+  // 3. 逐行提交（每行携带公共信息）
   submitLoading.value = true
   let successCount = 0
-  // ★ 生成批次号：同一批提交的所有记录共享，便于审批端按批次查看/统计
-  const batchNo = generateBatchNo()
   try {
     for (const row of validItems) {
       const payload: any = {
-        batch_no: batchNo,
         name: row.name,
         spec_model: row.spec_model,
         quantity: row.quantity,