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/pages/PageComposeClient.tsx

@@ -11,6 +11,7 @@ import {
   type SitePageInput,
 } from "@/lib/api";
 import { sitePagePublicPath, sitePagePublicURL } from "@/lib/sitePagePath";
+import { useUrlStyle } from "@/components/SiteBrandProvider";
 import { toast } from "@/lib/toast";
 import MarkdownEditor from "@/components/MarkdownEditor";
 import { AdminField, AdminSegmented, AdminStatusChip, AdminSwitch } from "@/components/admin";
@@ -129,6 +130,7 @@ export default function PageComposeClient({
 }) {
   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]);
@@ -160,7 +162,7 @@ export default function PageComposeClient({
   };
 
   const slugPreview = normalizeSlug(form.slug);
-  const publicPath = sitePagePublicPath(slugPreview);
+  const publicPath = sitePagePublicPath(slugPreview, urlStyle);
   const canViewOnline = savedPage?.published === true;
 
   async function commit() {
@@ -252,7 +254,7 @@ export default function PageComposeClient({
       setErrors((prev) => ({ ...prev, slug: nextErrors.slug }));
       return;
     }
-    const url = sitePagePublicURL(origin || window.location.origin, slug);
+    const url = sitePagePublicURL(origin || window.location.origin, slug, urlStyle);
     try {
       await navigator.clipboard.writeText(url);
       toast("已复制访问地址", "ok");
@@ -280,7 +282,7 @@ export default function PageComposeClient({
   }
   if (pendingSave?.slugChange) {
     confirmBits.push(
-      `访问地址将从 ${sitePagePublicPath(baseline.slug)} 改为 ${sitePagePublicPath(normalizeSlug(form.slug))}。系统不会把旧地址转到新地址，已经分享的旧链接会打不开。`
+      `访问地址将从 ${sitePagePublicPath(baseline.slug, urlStyle)} 改为 ${sitePagePublicPath(normalizeSlug(form.slug), urlStyle)}。系统不会把旧地址转到新地址，已经分享的旧链接会打不开。`
     );
   }
 
@@ -304,7 +306,7 @@ export default function PageComposeClient({
           <div className="admin-doc-sticky-actions">
             {canViewOnline && savedPage ? (
               <a
-                href={sitePagePublicPath(savedPage.slug)}
+                href={sitePagePublicPath(savedPage.slug, urlStyle)}
                 target="_blank"
                 rel="noopener noreferrer"
                 className="btn btn-line btn-sm"
@@ -413,7 +415,7 @@ export default function PageComposeClient({
               </div>
               <p className="admin-doc-hint" id="page-slug-hint">
                 完整路径 {publicPath || "/p/"}。小写字母、数字和连字符，最多 64 字符。
-                {origin && slugPreview ? ` 线上地址 ${sitePagePublicURL(origin, slugPreview)}` : ""}
+                {origin && slugPreview ? ` 线上地址 ${sitePagePublicURL(origin, slugPreview, urlStyle)}` : ""}
               </p>
               {isEdit && baseline.published && slugPreview !== baseline.slug ? (
                 <p className="admin-doc-hint">保存后访问地址会改变。旧链接不会自动跳转。</p>