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/announcements/page.tsx

@@ -15,6 +15,7 @@ import {
 } from "@/components/site-doc";
 import { requestCanonical } from "@/lib/canonicalMeta";
 import { canonicalPage } from "@/lib/siteUrl";
+import { announcementPath, type UrlStyle } from "@/lib/urlStyle";
 
 interface PageProps {
   searchParams: Promise<{ page?: string }>;
@@ -42,11 +43,11 @@ function plainSummary(md: string, max = 120): string {
   return text.length > max ? `${text.slice(0, max)}…` : text;
 }
 
-function FeaturedAnnouncement({ a }: { a: Announcement }) {
+function FeaturedAnnouncement({ a, urlStyle }: { a: Announcement; urlStyle: UrlStyle }) {
   const summary = plainSummary(a.content, 180);
   return (
     <Link
-      href={`/announcement/${a.id}`}
+      href={announcementPath(urlStyle, a.id)}
       className="block px-5 sm:px-6 pt-5 sm:pt-6 pb-5 transition-colors hover:bg-[var(--panel-2)] focus-visible:bg-[var(--panel-2)]"
     >
       <div className="flex items-center gap-2 flex-wrap mb-3">
@@ -77,11 +78,11 @@ function FeaturedAnnouncement({ a }: { a: Announcement }) {
   );
 }
 
-function AnnouncementRow({ a, showDivider }: { a: Announcement; showDivider: boolean }) {
+function AnnouncementRow({ a, showDivider, urlStyle }: { a: Announcement; showDivider: boolean; urlStyle: UrlStyle }) {
   const summary = plainSummary(a.content);
   return (
     <Link
-      href={`/announcement/${a.id}`}
+      href={announcementPath(urlStyle, a.id)}
       className="block px-5 sm:px-6 py-4 sm:py-5 transition-colors hover:bg-[var(--panel-2)] focus-visible:bg-[var(--panel-2)]"
       style={showDivider ? { borderTop: "1px solid var(--line)" } : undefined}
     >
@@ -131,6 +132,7 @@ export default async function AnnouncementsListPage({ searchParams }: PageProps)
   ]);
   const sidebarPages = overview?.sidebar_pages ?? [];
   const siteLead = settings.site_description?.trim() || undefined;
+  const urlStyle = settings.url_style;
   const canManagePages = !!me.user && isAdminOrAbove(me.user.role);
 
   // 首页置顶条目作头图；其余走列表行（置顶已在头图时不再重复）
@@ -178,9 +180,9 @@ export default async function AnnouncementsListPage({ searchParams }: PageProps)
           </div>
         ) : (
           <>
-            {featured ? <FeaturedAnnouncement a={featured} /> : null}
+            {featured ? <FeaturedAnnouncement a={featured} urlStyle={urlStyle} /> : null}
             {rest.map((a, i) => (
-              <AnnouncementRow key={a.id} a={a} showDivider={!!featured || i > 0} />
+              <AnnouncementRow key={a.id} a={a} showDivider={!!featured || i > 0} urlStyle={urlStyle} />
             ))}
           </>
         )}