feat: 公文三栏单页布局，并修复时间线目录跳转与样式

公告/单页对齐帖子详情三栏壳；时间线按日锚点可跳转，条目改为日志行并用暖金日期区分 feat 色。

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

frontend/app/page.tsx

@@ -83,7 +83,8 @@ export default async function HomePage({ searchParams }: HomePageProps) {
   const isSearch = keyword.length > 0;
 
   const cookie = authCookieHeader(await cookies());
-  const allowComments = (await getPublicSettingsCached()).allow_comments !== false;
+  const publicSettings = await getPublicSettingsCached();
+  const allowComments = publicSettings.allow_comments !== false;
   const sort = normalizeSort(sp.sort, allowComments);
   // 与 layout 共享同一份 /me 请求（React cache 去重）
   const mePromise = getMeCached(cookie || undefined);
@@ -240,6 +241,7 @@ export default async function HomePage({ searchParams }: HomePageProps) {
               allowComments={allowComments}
               canManageAnnouncements={canManageAnnouncements}
               sidebarPages={sidebarPages}
+              siteDescription={publicSettings.site_description}
             />
           )
         )}
@@ -273,6 +275,7 @@ export default async function HomePage({ searchParams }: HomePageProps) {
               allowComments={allowComments}
               canManageAnnouncements={canManageAnnouncements}
               sidebarPages={sidebarPages}
+              siteDescription={publicSettings.site_description}
             />
           </div>
         )