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/stores/auth/authStore.ts

@@ -265,7 +265,7 @@ export const useAuthStore = create<AuthState>((set) => ({
       // 7. 清除 sessionStore 的 userId
       useSessionStore.getState().setUserId(null);
       // 8. 清除 userManager 的内存缓存
-      const { userManager } = await import('../user');
+      const { userManager } = await import('../user/UserManager');
       userManager.invalidateUsers();
     } catch (error) {
       console.error('[AuthStore] 登出失败:', error);

src/stores/call/callStore.ts

@@ -10,7 +10,7 @@ import {
 import { webrtcManager, ICEServer } from '@/services/webrtc';
 import { getCurrentUserId } from '../auth/sessionStore';
 import { useUserStore } from '../userStore';
-import { userManager } from '../user';
+import { userManager } from '../user/UserManager';
 
 export type CallStatus = 
   | 'idle'           // 空闲状态

src/stores/user/hooks.ts

@@ -2,7 +2,7 @@ import { useCallback, useEffect, useRef } from 'react';
 import { useUserManagerStore } from './userStore';
 import { userManager } from './UserManager';
 import type { UserDTO } from '../../types/dto';
-import { useAuthStore } from '../auth/authStore';
+import { useSessionStore } from '../auth/sessionStore';
 
 export interface UseCurrentUserResult {
   user: UserDTO | null;
@@ -16,8 +16,7 @@ export function useCurrentUser(): UseCurrentUserResult {
   const lastFetchedRef = useRef<string | null>(null);
 
   useEffect(() => {
-    const authUser = useAuthStore.getState().currentUser;
-    const userId = authUser?.id;
+    const userId = useSessionStore.getState().userId;
     if (userId && lastFetchedRef.current !== userId) {
       lastFetchedRef.current = userId;
       useUserManagerStore.getState().setLoadingCurrentUser(true);
@@ -28,8 +27,8 @@ export function useCurrentUser(): UseCurrentUserResult {
   }, []);
 
   useEffect(() => {
-    return useAuthStore.subscribe((state, prev) => {
-      if (!state.currentUser && prev.currentUser) {
+    return useSessionStore.subscribe((state, prev) => {
+      if (!state.userId && prev.userId) {
         lastFetchedRef.current = null;
       }
     });

src/stores/userStore.ts

@@ -12,7 +12,7 @@ import {
   postService,
   notificationService,
 } from '../services';
-import { userManager } from './user';
+import { userManager } from './user/UserManager';
 import { messageManager } from './message';
 
 interface UserState {