feat: 关于本站对齐站点公告，增加全部与管理入口

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/app/sitemap.ts

@@ -1,5 +1,9 @@
 import type { MetadataRoute } from "next";
-import { fetchPosts, fetchAnnouncementsPage, fetchOverview } from "@/lib/api";
+import {
+  fetchPosts,
+  fetchAnnouncementsPage,
+  fetchPublishedSitePages,
+} from "@/lib/api";
 
 export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
   const baseUrl = "http://localhost:3000";
@@ -11,6 +15,12 @@ export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
       changeFrequency: "daily",
       priority: 0.7,
     },
+    {
+      url: `${baseUrl}/about`,
+      lastModified: new Date(),
+      changeFrequency: "monthly",
+      priority: 0.6,
+    },
   ];
 
   try {
@@ -41,13 +51,12 @@ export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
     /* 忽略 */
   }
 
-  // 公开单页列表 API 尚未提供：用 overview 侧栏页近似收录已发布且展示中的页面
   try {
-    const overview = await fetchOverview();
-    for (const p of overview.sidebar_pages ?? []) {
+    const { pages } = await fetchPublishedSitePages();
+    for (const p of pages) {
       entries.push({
         url: `${baseUrl}/p/${p.slug}`,
-        lastModified: new Date(),
+        lastModified: new Date(p.updated_at || p.created_at),
         changeFrequency: "monthly",
         priority: 0.4,
       });