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/u/[id]/page.tsx

@@ -28,6 +28,7 @@ import FollowButton from "@/components/FollowButton";
 import StaffUserMenu from "@/components/StaffUserMenu";
 import { requestCanonical } from "@/lib/canonicalMeta";
 import { absoluteCanonical, canonicalPage } from "@/lib/siteUrl";
+import { userPath } from "@/lib/urlStyle";
 import { profileJsonLd } from "@/lib/jsonLd";
 import JsonLd from "@/components/JsonLd";
 
@@ -52,7 +53,9 @@ export async function generateMetadata({ params, searchParams }: UserPageProps):
   const tab = parseTab(sp.tab);
   try {
     const data = await fetchUserProfile(id, 1);
-    const allowComments = (await getPublicSettingsCached()).allow_comments !== false;
+    const pub = await getPublicSettingsCached();
+    const allowComments = pub.allow_comments !== false;
+    const urlStyle = pub.url_style;
     const title = data.user.nickname || data.user.username;
     const description = allowComments
       ? `查看 ${data.user.nickname} 的资料、发帖与评论`
@@ -71,7 +74,7 @@ export async function generateMetadata({ params, searchParams }: UserPageProps):
     return {
       title,
       description,
-      ...(await requestCanonical(`/u/${data.user.id}`, query)),
+      ...(await requestCanonical(userPath(urlStyle, data.user.id), query)),
     };
   } catch {
     return { title: "用户不存在" };
@@ -93,6 +96,7 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
   const me = await getMeCached(cookie || undefined);
   const settings = await getPublicSettingsCached();
   const allowComments = settings.allow_comments !== false;
+  const urlStyle = settings.url_style;
   const commentsRequireLogin = settings.comments_require_login === true;
   const allowMessages = settings.allow_messages !== false;
   const canReadComments = allowComments && (!commentsRequireLogin || !!me.user);
@@ -206,7 +210,8 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
       ]
     : [];
   const visibleNav = [...mainNavItems, ...settingsNavItems];
-  const tabHref = (t: UserTab) => (t === "posts" ? `/u/${id}` : `/u/${id}?tab=${t}`);
+  const tabHref = (t: UserTab) =>
+    t === "posts" ? userPath(urlStyle, Number(id)) : `${userPath(urlStyle, Number(id))}?tab=${t}`;
 
   const profileQuery: Record<string, string | number> = {};
   if (canReadComments && effectiveTab === "comments") profileQuery.tab = "comments";
@@ -222,7 +227,8 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
           name: u.nickname || u.username,
           username: u.username,
           signature: (u.signature || "").trim() || undefined,
-          pageUrl: absoluteCanonical(`/u/${u.id}`, profileQuery),
+          pageUrl: absoluteCanonical(userPath(urlStyle, u.id), profileQuery),
+          urlStyle,
         });
 
   /** 本页卡片统一阴影；暗色随 color-mix 自动加深 */
@@ -255,12 +261,12 @@ export default async function UserPage({ params, searchParams }: UserPageProps)
         {/* 本人操作按钮 / 访客私聊：绝对定位在卡片右上角 */}
         {isOwner ? (
           <div className="absolute top-3 right-3 z-20 flex items-center gap-2">
-            <Link href={`/u/${id}?tab=settings`} className="btn btn-line btn-sm">
+            <Link href={`${userPath(urlStyle, Number(id))}?tab=settings`} className="btn btn-line btn-sm">
               <PenLine size={13.5} />
               <span className="hidden sm:inline">编辑资料</span>
             </Link>
             <Link
-              href={`/u/${id}?tab=security`}
+              href={`${userPath(urlStyle, Number(id))}?tab=security`}
               aria-label="安全设置"
               data-tip="安全设置"
               className="inline-flex w-8 h-8 items-center justify-center rounded-full border transition-colors duration-150 hover:border-[var(--accent)] hover:text-[var(--accent)]"