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/announcements/AnnouncementAdmin.tsx

@@ -13,6 +13,7 @@ import {
 import { formatDateTime, formatRelative } from "@/lib/format";
 import { toast } from "@/lib/toast";
 import ConfirmDialog from "@/components/ConfirmDialog";
+import { useUrlStyle } from "@/components/SiteBrandProvider";
 import {
   AdminEmpty,
   AdminPageHeader,
@@ -62,6 +63,7 @@ export default function AnnouncementAdmin({
 }) {
   const router = useRouter();
   const searchParams = useSearchParams();
+  const urlStyle = useUrlStyle();
   const statusFilter = readStatus(searchParams.get("status"));
   const [list, setList] = useState(initial);
   const [loadError, setLoadError] = useState(initError);
@@ -215,7 +217,7 @@ export default function AnnouncementAdmin({
                           <span className={`j13-anno-tag is-${a.tag_color}`} title={a.tag}>
                             {a.tag}
                           </span>
-                          {a.published ? <code>{announcementPublicPath(a.id)}</code> : null}
+                          {a.published ? <code>{announcementPublicPath(a.id, urlStyle)}</code> : null}
                         </p>
                         {summary ? <p className="admin-doc-excerpt" title={summary}>{summary}</p> : null}
                       </td>
@@ -241,7 +243,7 @@ export default function AnnouncementAdmin({
                           </Link>
                           {a.published ? (
                             <a
-                              href={announcementPublicPath(a.id)}
+                              href={announcementPublicPath(a.id, urlStyle)}
                               target="_blank"
                               rel="noopener noreferrer"
                               className="admin-doc-textbtn"

frontend/app/admin/announcements/AnnouncementComposeClient.tsx

@@ -15,6 +15,7 @@ import { toast } from "@/lib/toast";
 import MarkdownEditor from "@/components/MarkdownEditor";
 import { AdminField, AdminSegmented, AdminStatusChip, AdminSwitch } from "@/components/admin";
 import ConfirmDialog from "@/components/ConfirmDialog";
+import { useUrlStyle } from "@/components/SiteBrandProvider";
 import useUnsavedGuard from "@/hooks/useUnsavedGuard";
 import { ANNOUNCEMENT_COLORS, announcementPublicPath } from "./announcementColors";
 
@@ -117,6 +118,7 @@ export default function AnnouncementComposeClient({
 }) {
   const router = useRouter();
   const searchParams = useSearchParams();
+  const urlStyle = useUrlStyle();
   const status = readStatus(searchParams.get("status"));
   const backHref = listHref(status);
   const loaded = useMemo(() => toForm(initial), [initial]);
@@ -146,7 +148,7 @@ export default function AnnouncementComposeClient({
   };
 
   const canViewOnline = saved?.published === true && saved.id > 0;
-  const publicPath = saved ? announcementPublicPath(saved.id) : "";
+  const publicPath = saved ? announcementPublicPath(saved.id, urlStyle) : "";
 
   async function commit() {
     if (saving) return;
@@ -227,7 +229,7 @@ export default function AnnouncementComposeClient({
 
   async function copyAddress() {
     if (!saved) return;
-    const url = `${(origin || window.location.origin).replace(/\/$/, "")}${announcementPublicPath(saved.id)}`;
+    const url = `${(origin || window.location.origin).replace(/\/$/, "")}${announcementPublicPath(saved.id, urlStyle)}`;
     try {
       await navigator.clipboard.writeText(url);
       toast("已复制访问地址", "ok");

frontend/app/admin/announcements/announcementColors.ts

@@ -1,4 +1,5 @@
 import type { AnnouncementColor } from "@/lib/api";
+import { announcementPath, type UrlStyle } from "@/lib/urlStyle";
 
 /** 标签色板：与后端 AnnouncementColor 白名单一致（12 色） */
 export const ANNOUNCEMENT_COLORS: { value: AnnouncementColor; label: string }[] = [
@@ -17,6 +18,6 @@ export const ANNOUNCEMENT_COLORS: { value: AnnouncementColor; label: string }[]
 ];
 
 /** 公告公开路径。前台是 /announcement/[id]，列表和线上查看用同一条。 */
-export function announcementPublicPath(id: number): string {
-  return `/announcement/${id}`;
+export function announcementPublicPath(id: number, urlStyle: UrlStyle = "default"): string {
+  return announcementPath(urlStyle, id);
 }