feat: add batch-delete API endpoint, replace N+1 frontend calls

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/frontend/src/views/files/Orders.vue

@@ -223,15 +223,15 @@ async function batchDownload() {
 async function batchDelete() {
   try {
     await ElMessageBox.confirm(`确定删除选中的 ${selected.value.length} 个文件？`, '确认')
-    for (const row of selected.value) {
-      if (row.result_purchase) {
-        await api.delete(`/files/result/${encodeURIComponent(row.result_purchase)}`)
-      }
-      if (row.id) {
-        await api.delete('/files/relations', { data: { ids: [row.id] } })
-      }
+    const files = selected.value
+      .filter(r => r.result_purchase)
+      .map(r => ({ directory: 'result', filename: r.result_purchase }))
+    const res = await api.post('/files/batch-delete', { files })
+    if (res.data.errors?.length) {
+      ElMessage.warning(`删除完成，${res.data.errors.length} 个文件失败`)
+    } else {
+      ElMessage.success('批量删除完成')
     }
-    ElMessage.success('批量删除完成')
     loadData()
   } catch (err: any) {
     if (err !== 'cancel') ElMessage.error('批量删除失败')