Footer: add Claude Code credit

Author: herilalaina

index.html

@@ -586,6 +586,7 @@ <h2 class="title">BibTeX</h2>
               Source for this site is available on <a href="https://github.com/automl/AlphaPFN" target="_blank">GitHub</a>.
             </p>
             <p style="font-size: 0.9rem; color:#6b7280;">
+              Designed with <a href="https://claude.com/claude-code" target="_blank">Claude Code</a>.
               Licensed under
               <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/" target="_blank">CC BY-SA 4.0</a>.
             </p>