Update the footer to center text for small displays.

lib/decentralised_book_index_web/components/my_partials/footer.ex

@@ -6,7 +6,7 @@ defmodule DecentralisedBookIndexWeb.Components.MyPartials.Footer do
     <footer class="bg-white shadow-sm dark:bg-gray-900">
       <div class="w-full max-w-screen-xl mx-auto p-4 md:py-8">
         <hr class="my-6 border-gray-200 sm:mx-auto dark:border-gray-700 lg:my-8" />
-        <span class="block text-sm text-gray-500 sm:text-center dark:text-gray-400">© 2025 Kostiantyn Klochko. All Rights Reserved.</span>
+        <span class="block text-sm text-gray-500 text-center dark:text-gray-400">© 2025 Kostiantyn Klochko. All Rights Reserved.</span>
       </div>
     </footer>
     """