fix: 修复批量删除 undefined/失败问题（POST 替代 DELETE body）

- 批量删除改走 POST /users/batch-remove（稳定保证 body 可被 Express 解析），同时增强 DELETE /batch 兼容 query string 回退
- 前端 usersApi.batchRemove 改用 POST 请求；批量删除函数新增 ok 标志位校验 + ?? 0 防 undefined，catch 分支带前缀明确提示失败原因
- npm run build 通过

client/src/api/index.ts

@@ -66,11 +66,7 @@ export const usersApi = {
       results: Array<{ idx: number; ok: boolean; id?: number; error?: string; item: any }>;
     }>('/users/batch', { items }).then(r => r.data),
   batchRemove: (ids: number[]) =>
-    api.request<{ ok: boolean; deleted: number; total: number }>({
-      url: '/users/batch',
-      method: 'DELETE',
-      data: { ids },
-    }).then(r => r.data),
+    api.post<{ ok: boolean; deleted: number; total: number }>('/users/batch-remove', { ids }).then(r => r.data),
 };
 
 export const activitiesApi = {

client/src/pages/admin/Users.tsx

@@ -165,11 +165,15 @@ export default function Users() {
     if (!confirm(`确认删除选中的 ${selectedCount} 名部员？相关的时长登记也会一并删除，此操作不可撤销。`)) return;
     try {
       const result = await usersApi.batchRemove(Array.from(selectedIds));
-      alert(`批量删除完成：共提交 ${result.total} 条，实际删除 ${result.deleted} 条`);
+      if (!result || result.ok === false) {
+        alert('批量删除失败：' + ((result as any)?.error || '未知错误'));
+        return;
+      }
+      alert(`批量删除完成：共提交 ${result.total ?? 0} 条，实际删除 ${result.deleted ?? 0} 条`);
       clearSelection();
       load();
     } catch (e) {
-      alert(errMsg(e));
+      alert('批量删除失败：' + errMsg(e));
     }
   };