style(web): tidy the homepage QQ group caption

Drops the fa-qq penguin icon and the "扫码加入，或搜索群号" call-to-action
in favor of a plain "QQ群号：575404333" label — the QR right above already
implies scanning, and the column header names the group.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/app/page.tsx

@@ -731,7 +731,7 @@ export default function HomePage() {
               className="mx-auto mb-3 w-32 max-w-full rounded-sm border border-clay-900/10 shadow-sm shadow-clay-900/5"
             />
             <p className="font-serif text-clay-700 text-base leading-relaxed">
-              <i className="fa-brands fa-qq text-[15px] text-clay-500" /> 扫码加入，或搜索群号{" "}
+              QQ群号：
               <span className="font-sans text-sm text-clay-900">575404333</span>
             </p>
           </div>