Add footer with company name (SDJ Labs Co., Ltd.)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/app/page.tsx

@@ -850,6 +850,11 @@ export default function Home() {
           )}
         </BottomSheet>
       </div>
+
+      {/* Footer */}
+      <footer className="shrink-0 border-t bg-gray-50 py-2 text-center text-[11px] text-gray-400">
+        SDJ Labs Co., Ltd.
+      </footer>
     </div>
   );
 }