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/components/admin/AdminShell.tsx

@@ -48,6 +48,8 @@ import Avatar from "@/components/Avatar";
 import RoleBadge from "@/components/RoleBadge";
 import NotificationBell from "@/components/NotificationBell";
 import ThemeToggle from "@/components/ThemeToggle";
+import { useUrlStyle } from "@/components/SiteBrandProvider";
+import { userPath } from "@/lib/urlStyle";
 
 interface NavItem {
   href: string;
@@ -294,6 +296,7 @@ function AdminRailNav({
 }
 
 function AdminUserMenu({ user, onLogout }: { user: User; onLogout: () => void }) {
+  const urlStyle = useUrlStyle();
   const [open, setOpen] = useState(false);
   const menuRef = useRef<HTMLDivElement>(null);
 
@@ -375,7 +378,7 @@ function AdminUserMenu({ user, onLogout }: { user: User; onLogout: () => void })
             </div>
           </div>
           <div className="p-1.5">
-            <Link href={`/u/${user.id}`} onClick={() => setOpen(false)} className={itemCls} role="menuitem">
+            <Link href={userPath(urlStyle, user.id)} onClick={() => setOpen(false)} className={itemCls} role="menuitem">
               <UserIcon size={15} style={{ color: "var(--ink-3)" }} /> 个人主页
             </Link>
             <Link href="/settings" onClick={() => setOpen(false)} className={itemCls} role="menuitem">