fix: 批量添加工工作组调试回显 + 完整验证写入

- 后端 /users/batch 返回每条成功记录的 groups_written/groups_expected/group_ids_out；失败记录返回 group_ids_seen/count
- 前端 submitBatch：console.log 打印发送 payload 和响应；弹窗汇总工作组实际/期望写入数；任何异常的行都显示后端实际解析出的 group_ids_out，失败行同时显示后端收到的 group_ids_seen
- 本地模拟后端 sql.js 写入 user_groups 100% 正确（场景A/B测试均 changes=1，聚合查询正确），此提交部署后通过控制台和弹窗即可精确定位问题在哪一跳（前端发送 vs 后端解析 vs 数据库写入）
- npm run build 通过

client/src/pages/admin/Users.tsx

@@ -349,18 +349,29 @@ export default function Users() {
         volunteer_no: r.volunteer_no || null,
         group_ids: r.group_ids,
       }));
+      console.log('[DEBUG] batch payload items (first 3):', JSON.stringify(items.slice(0, 3), null, 2));
       const result = await usersApi.batch(items);
+      console.log('[DEBUG] batch response:', result);
       setBatchErrors('');
-      const msg = `批量添加完成：共 ${result.total} 条，成功 ${result.success} 条，失败 ${result.failed} 条`;
+      const totalActualWritten = result.results.filter(r => r.ok).reduce((sum: number, r: any) => sum + (r?.groups_written ?? 0), 0);
+      const totalExpectedWritten = result.results.filter(r => r.ok).reduce((sum: number, r: any) => sum + (r?.groups_expected ?? 0), 0);
+      const msg = `批量添加完成：共 ${result.total} 条，成功 ${result.success} 条，失败 ${result.failed} 条
+工作组写入：实际 ${totalActualWritten} 条，期望 ${totalExpectedWritten} 条`;
       if (result.failed === 0) {
-        alert(msg);
+        const mis = result.results.filter((r: any) => r.ok && (r?.groups_written ?? 0) !== (r?.groups_expected ?? 0));
+        if (mis.length === 0) {
+          alert(msg);
+        } else {
+          const lines = mis.slice(0, 20).map((r: any) => `第${r.idx + 1}行 ${r.item.name}：期望 ${r.groups_expected} 组，实际写入 ${r.groups_written} 组（后端解析 group_ids_out=${JSON.stringify(r.group_ids_out ?? [])}）`).join('\n');
+          alert(`${msg}\n\n工作组未全部写入（前20）：\n${lines}`);
+        }
         setBatchOpen(false);
         setBatchText('');
         load();
       } else {
         const failLines = result.results
           .filter((r) => !r.ok)
-          .map((r) => `第${r.idx + 1}行 [${r.item.class} ${r.item.name}]：${r.error}`)
+          .map((r: any) => `第${r.idx + 1}行 [${r.item.class} ${r.item.name}]：${r.error}（后端接收 group_ids_count=${r.group_ids_count ?? 'N/A'}，内容=${JSON.stringify(r.group_ids_seen ?? null)}）`)
           .join('\n');
         alert(`${msg}\n\n失败明细：\n${failLines}`);
         load();