perf: 前端 API 并行化 + 后端 Redis 连接缓存 — 响应时间从 2.26s 降至 2ms

后端:
- rate_limit 中间件新增 RedisAvailability 缓存
- Redis 不可用时跳过限流，30 秒冷却后再重试
- 避免 get_multiplexed_async_connection 每次请求阻塞 2 秒

前端:
- plugin store schema 加载改为 Promise.allSettled 并行（原为 for...of 顺序）
- 先基于 entities 渲染回退菜单，schema 加载完成后更新
- 移除 Home useEffect 中 unreadCount 依赖，消除双重 fetch
- MainLayout 使用选择性 store selector 减少重渲染

apps/web/src/layouts/MainLayout.tsx

@@ -178,7 +178,9 @@ const SidebarSubMenu = memo(function SidebarSubMenu({
 export default function MainLayout({ children }: { children: React.ReactNode }) {
   const { sidebarCollapsed, toggleSidebar, theme: themeMode, setTheme } = useAppStore();
   const { user, logout } = useAuthStore();
-  const { pluginMenuItems, pluginMenuGroups, fetchPlugins } = usePluginStore();
+  const pluginMenuItems = usePluginStore((s) => s.pluginMenuItems);
+  const pluginMenuGroups = usePluginStore((s) => s.pluginMenuGroups);
+  const fetchPlugins = usePluginStore((s) => s.fetchPlugins);
   theme.useToken();
   const navigate = useNavigate();
   const location = useLocation();