fix: enhance pagination settings across multiple pages with default size and options

apps/admin/src/pages/Teachers/index.tsx

@@ -46,13 +46,14 @@ const ROLE_TYPE_LABELS: Record<string, string> = {
   academic_teacher: '教务老师',
 };
 
-const PAGE_SIZE = 20;
+const DEFAULT_PAGE_SIZE = 20;
 
 const TeachersPage: React.FC = () => {
   const [data, setData] = useState<TeacherRow[]>([]);
   const [loading, setLoading] = useState(false);
   const [total, setTotal] = useState(0);
   const [page, setPage] = useState(1);
+  const [pageSize, setPageSize] = useState(DEFAULT_PAGE_SIZE);
   const [search, setSearch] = useState('');
   const [profileModal, setProfileModal] = useState<TeacherRow | null>(null);
   const [form] = Form.useForm<ProfileFormValues>();
@@ -62,7 +63,7 @@ const TeachersPage: React.FC = () => {
     setLoading(true);
     try {
       const res = await api.get<TeacherListResponse>('/rbac/teachers', {
-        params: { search: search || undefined, page, pageSize: PAGE_SIZE },
+        params: { search: search || undefined, page, pageSize },
       });
       setData(res.list);
       setTotal(res.total);
@@ -70,7 +71,7 @@ const TeachersPage: React.FC = () => {
       // silent
     }
     setLoading(false);
-  }, [page, search]);
+  }, [page, pageSize, search]);
 
   useEffect(() => {
     fetchData();
@@ -199,9 +200,14 @@ const TeachersPage: React.FC = () => {
         scroll={{ x: 1300 }}
         pagination={{
           current: page,
-          pageSize: PAGE_SIZE,
+          pageSize,
           total,
-          onChange: setPage,
+          showSizeChanger: true,
+          pageSizeOptions: [20, 50, 100],
+          onChange: (nextPage, nextPageSize) => {
+            setPage(nextPage);
+            setPageSize(nextPageSize);
+          },
           showTotal: (t) => `共 ${t} 人`,
         }}
         expandable={{