add mobile settings navigation

app/views/settings_index/index.html.erb

@@ -0,0 +1,7 @@
+<div class="mb-2 w-full">
+  <a href="<%= root_path %>" class="flex items-center space-x-0.5 font-medium">
+    <%= svg_icon('arrow_left', class: 'w-4 h-4 stroke-2') %>
+    <span><%= t('back') %></span>
+  </a>
+</div>
+<%= render 'shared/settings_nav', expanded: true %>