feat: 交付官方 Docker 运行时，外观改背景图并下线自定义 CSS/JS

站点/后台分轨背景与用户列表排序一并落地；生产 CORS 改走 SITE_URL，健康检查带版本号。

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

frontend/app/announcement/[id]/page.tsx

@@ -105,15 +105,6 @@ export default async function AnnouncementPage({ params }: PageProps) {
       <SiteDocShell
         left={left}
         right={right}
-        breadcrumb={
-          <SiteDocBreadcrumb
-            items={[
-              { href: "/", label: "首页" },
-              { href: "/announcements", label: "站点公告" },
-              { label: a.title },
-            ]}
-          />
-        }
         mobileExtras={
           <>
             {toc.length > 0 ? <PostToc items={toc} /> : null}
@@ -123,6 +114,14 @@ export default async function AnnouncementPage({ params }: PageProps) {
         }
       >
         <article className="panel p-6 sm:p-8">
+          <SiteDocBreadcrumb
+            className="is-ruled"
+            items={[
+              { href: "/", label: "首页" },
+              { href: "/announcements", label: "站点公告" },
+              { label: a.title },
+            ]}
+          />
           <SiteDocMasthead
             kicker="站点公告"
             title={a.title}