feat: 可配置站点 URL 风格

- 新增 urlStyle 工具与测试：postPath/userPath/sitePagePath 统一生成链接
- 管理端新增 UrlStylePanel 设置面板，settings 服务与 handler 适配
- 全站路由链接与 JSON-LD/sitemap 切换为统一 URL 生成
- middleware 与相关组件适配

frontend/app/notifications/NotificationsClient.tsx

@@ -5,12 +5,15 @@ import { useRouter } from "next/navigation";
 import Link from "next/link";
 import { Heart, MessageCircle, CheckCheck, Bell, CheckCircle2, XCircle, AtSign, ClipboardList, Award, AlertTriangle, UserPlus } from "lucide-react";
 import { apiMarkRead, apiMarkAllRead, type NotificationsResponse, type NotificationItem } from "@/lib/api";
+import { useUrlStyle } from "@/components/SiteBrandProvider";
+import { postPath, userPath } from "@/lib/urlStyle";
 
 /**
  * 通知列表交互层：数据由服务端 SSR 直出，这里只承担已读标记等客户端操作。
  */
 export default function NotificationsClient({ initialData }: { initialData: NotificationsResponse }) {
   const router = useRouter();
+  const urlStyle = useUrlStyle();
   const [notifications, setNotifications] = useState<NotificationItem[]>(initialData.notifications || []);
 
   const handleClick = async (n: NotificationItem) => {
@@ -24,16 +27,16 @@ export default function NotificationsClient({ initialData }: { initialData: Noti
     if (n.type === "mention" && n.room_id) {
       router.push(`/chat/${n.room_id}`);
     } else if (n.type === "pending_review") {
-      router.push(n.post_id ? `/post/${n.post_id}` : "/admin/content?status=pending");
+      router.push(n.post_id ? postPath(urlStyle, n.post_id) : "/admin/content?status=pending");
     } else if (n.type === "badge") {
       return;
     } else if (n.type === "follow") {
-      router.push(`/u/${n.actor_id}`);
+      router.push(userPath(urlStyle, n.actor_id));
     } else if (n.comment_id > 0) {
       // 评论/回复/点赞等：直达评论所在楼层（跨页由帖子页深链定位换页）
-      router.push(`/post/${n.post_id}#comment-${n.comment_id}`);
+      router.push(`${postPath(urlStyle, n.post_id)}#comment-${n.comment_id}`);
     } else {
-      router.push(`/post/${n.post_id}`);
+      router.push(postPath(urlStyle, n.post_id));
     }
   };
 
@@ -151,7 +154,7 @@ export default function NotificationsClient({ initialData }: { initialData: Noti
                   ) : (
                     <>
                       <Link
-                        href={`/u/${n.actor.id}`}
+                        href={userPath(urlStyle, n.actor.id)}
                         onClick={(e) => e.stopPropagation()}
                         className="font-semibold hover:text-[var(--accent)] transition-colors"
                       >