Add the footer partial.

lib/decentralised_book_index_web/components/layouts/app.html.heex

@@ -8,3 +8,5 @@
     {@inner_content}
   </div>
 </main>
+
+<.partial_footer />

lib/decentralised_book_index_web/components/my_partials.ex

@@ -4,6 +4,7 @@ defmodule DecentralisedBookIndexWeb.Components.MyPartials do
   defmacro __using__(_) do
     quote do
       import MyPartials.Navbar, only: [partial_navbar: 1]
+      import MyPartials.Footer, only: [partial_footer: 1]
     end
   end
 end

lib/decentralised_book_index_web/components/my_partials/footer.ex

@@ -0,0 +1,22 @@
+defmodule DecentralisedBookIndexWeb.Components.MyPartials.Footer do
+  use Phoenix.Component
+
+  def partial_footer(assigns) do
+    ~H"""
+    <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>
+      </div>
+    </footer>
+    """
+  end
+
+  def selected_navbar_link_css(page_title, active_title) do
+    if active_title =~ page_title do
+      "block py-2 pr-4 pl-3 text-black dark:text-white rounded bg-primary-700 lg:bg-transparent lg:text-primary-700 lg:p-0 dark:text-white"
+    else
+      "block py-2 pr-4 pl-3 text-gray-700 border-b border-gray-100 hover:bg-gray-50 lg:hover:bg-transparent lg:border-0 lg:hover:text-primary-700 lg:p-0 dark:text-gray-400 lg:dark:hover:text-white dark:hover:bg-gray-700 dark:hover:text-white lg:dark:hover:bg-transparent dark:border-gray-700"
+    end
+  end
+end