公开页补齐自引用 Canonical 与按类型的结构化数据，图片补上说明文字。

后台设置和内容编辑改成可导航布局；部署用访客 origin 生成 Canonical，避免落到容器地址。

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

frontend/app/robots.ts

@@ -1,11 +1,15 @@
 import type { MetadataRoute } from "next";
+import { connection } from "next/server";
+import { resolveSiteOrigin } from "@/lib/siteUrl";
 
-export default function robots(): MetadataRoute.Robots {
+export default async function robots(): Promise<MetadataRoute.Robots> {
+  await connection();
+  const origin = resolveSiteOrigin();
   return {
     rules: {
       userAgent: "*",
       allow: "/",
     },
-    sitemap: "http://localhost:3000/sitemap.xml",
+    ...(origin ? { sitemap: `${origin}/sitemap.xml` } : {}),
   };
 }