feat(frontend+backend): 实现SSR登录态优化与字体自托管

1. 后端调整refresh cookie路径与注释，完善认证cookie处理逻辑
2. 前端全局layout新增next/font自托管字体，消除FOUT闪动
3. 实现SSR直出登录态与未读通知数，避免页面加载闪动
4. 新增中间件处理access token静默轮转，保障SSR登录态
5. 优化登录、改密流程，添加页面刷新同步登录态
6. 重构通知铃铛组件支持初始未读数传入

frontend/components/NotificationBell.tsx

@@ -12,10 +12,11 @@ import {
   type NotificationItem,
 } from "@/lib/api";
 
-export default function NotificationBell() {
+export default function NotificationBell({ initialUnread = 0 }: { initialUnread?: number }) {
   const router = useRouter();
   const [open, setOpen] = useState(false);
-  const [unread, setUnread] = useState(0);
+  // SSR 直出未读数，红点不再挂载后才弹出；挂载后轮询自然校正
+  const [unread, setUnread] = useState(initialUnread);
   const [notifications, setNotifications] = useState<NotificationItem[]>([]);
   const [loading, setLoading] = useState(false);
   const dropdownRef = useRef<HTMLDivElement>(null);