chore: 去掉未上线前的旧兼容垫片，板块流收口到首页

鉴权只认 cookie、SEO 只走 Next、sort 与推荐对齐；删除 Bearer、Go sitemap、post_type 回填等冗余路径。

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

frontend/components/PostRow.tsx

@@ -91,7 +91,7 @@ export default function PostRow({
           }`}
         >
           {boardHref && (
-            <Link href={`/board/${post.board.id}`} className="j13-board-tag">
+            <Link href={`/?board=${post.board.id}`} className="j13-board-tag">
               {post.board.name}
             </Link>
           )}