polish(ui): 侧栏可点块悬停/聚焦统一为主题色淡底

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

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

@@ -290,10 +290,7 @@ function RelatedPosts({
             <Link href={`/post/${p.id}`} className="j13-rank" data-tip={p.title}>
               <span className="j13-rank-no">{i + 1}</span>
               <span className="min-w-0 flex-1">
-                <span
-                  className="block text-[13px] leading-snug line-clamp-2"
-                  style={{ color: "var(--ink)" }}
-                >
+                <span className="j13-rank-title line-clamp-2">
                   {p.title}
                 </span>
                 <span className="mt-1 flex items-center gap-2.5 meta text-[11.5px]">