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/admin/users/UsersAdmin.tsx

@@ -36,6 +36,8 @@ import {
 import { isOwner, ROLES } from "@/lib/roles";
 import { formatDate, formatRelative } from "@/lib/format";
 import { realtime } from "@/lib/realtime";
+import { userPath } from "@/lib/urlStyle";
+import { useUrlStyle } from "@/components/SiteBrandProvider";
 import Avatar from "@/components/Avatar";
 import RoleBadge from "@/components/RoleBadge";
 import Modal from "@/components/Modal";
@@ -302,6 +304,7 @@ export default function UsersAdmin({
   currentUserId: number;
   currentUserRole: string;
 }) {
+  const urlStyle = useUrlStyle();
   const [users, setUsers] = useState<AdminUser[]>(initial?.users ?? []);
   const [summary, setSummary] = useState<AdminUserSummary>(
     initial?.summary ?? {
@@ -686,7 +689,7 @@ export default function UsersAdmin({
       return (
         <div className="flex items-center gap-1.5 flex-wrap">
           {auditBtn}
-          <Link href={`/u/${u.id}`} className="btn btn-line btn-sm gap-1" aria-label={`查看 ${u.nickname} 的个人主页`}>
+          <Link href={userPath(urlStyle, u.id)} className="btn btn-line btn-sm gap-1" aria-label={`查看 ${u.nickname} 的个人主页`}>
             <ExternalLink size={13} />
             主页
           </Link>
@@ -697,7 +700,7 @@ export default function UsersAdmin({
       return (
         <div className="flex items-center gap-1.5 flex-wrap">
           {auditBtn}
-          <Link href={`/u/${u.id}`} className="btn btn-line btn-sm gap-1" aria-label={`查看 ${u.nickname} 的个人主页`}>
+          <Link href={userPath(urlStyle, u.id)} className="btn btn-line btn-sm gap-1" aria-label={`查看 ${u.nickname} 的个人主页`}>
             <ExternalLink size={13} />
             主页
           </Link>
@@ -718,7 +721,7 @@ export default function UsersAdmin({
     return (
       <div className="flex items-center gap-1.5 flex-wrap">
         {auditBtn}
-        <Link href={`/u/${u.id}`} className="btn btn-line btn-sm gap-1" aria-label={`查看 ${u.nickname} 的个人主页`}>
+        <Link href={userPath(urlStyle, u.id)} className="btn btn-line btn-sm gap-1" aria-label={`查看 ${u.nickname} 的个人主页`}>
           <ExternalLink size={13} />
           主页
         </Link>