Add footer component and styles to prevent overlap with content

Frontend/src/App.jsx

@@ -5,6 +5,13 @@ function App() {
   return (
     <div className="App">
       <CodeChallenge />
+      <footer className="footer-bar fixed bottom-0 left-0 right-0 border-t border-slate-200/40 dark:border-gray-800/20 bg-black">
+        <div className="flex items-center justify-center h-7">
+          <span className="text-xs text-slate-400 dark:text-gray-400 flex items-center">
+            Copyright © 2025. Made with <span className="text-red-400 dark:text-red-500 mx-0.5">♡</span> by Ishika and Arnab.
+          </span>
+        </div>
+      </footer>
     </div>
   )
 }