⚡️ perf(chat): 优化聊天消息加载性能

- 将聊天消息分页大小从200调整为30，减少初始加载数据量
- 提升课堂聊天界面加载速度和响应性能

src/client/mobile/components/Classroom/useClassroom.ts

@@ -740,7 +740,7 @@ export const useClassroom = ({ user }:{ user : User }) => {
         const response = await chatMessageClient.$get({
           query: {
             page: 1,
-            pageSize: 200,
+            pageSize: 30,
             filters: JSON.stringify({classId}),
             sortBy: 'timestamp',
             sortOrder: 'DESC'