feat(ui): add emoji picker with FlatList virtualization and improve input components

- Add full emoji picker with virtualized FlatList to CreatePostScreen and PostDetailScreen
- Add autoExpand prop to PostMentionInput for XHS-style content area
- Improve mention item styling with @ icon and hint text
- Fix HomeScreen tab switching race condition with requestAnimationFrame
- Fix PostRepository pagination to prefer cursor over page parameter
- Fix user store imports to use explicit UserManager path
- Refactor useCurrentUser hook to use sessionStore directly

src/screens/home/HomeScreen.tsx

@@ -439,8 +439,18 @@ export const HomeScreen: React.FC = () => {
 
   // Tab 切换时刷新数据并重置列表
   useEffect(() => {
-    reset();
-    refresh();
+    let cancelled = false;
+    const run = async () => {
+      reset();
+      // reset 会清空 store 中的状态，但异步订阅可能有延迟；
+      // 等一帧确保 store 的订阅回调已传播到 useDifferentialPosts
+      await new Promise(resolve => requestAnimationFrame(resolve));
+      if (!cancelled) {
+        await refresh();
+      }
+    };
+    run();
+    return () => { cancelled = true; };
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [activeIndex, currentChannelId]);