style: adjust font size in footer container

- Change font size from 'text-sm' to 'text-xs' for better visibility

This adjustment improves the aesthetics of the footer by ensuring that the
text is appropriately sized and matches the overall design of the page.

app/views/layouts/application.html.erb

@@ -76,7 +76,7 @@
   <!-- 页脚 -->
   <footer class="footer footer-center p-8 bg-base-200 text-base-content">
     <div class="container mx-auto flex flex-col gap-2">
-      <div id="busuanzi_container" class="text-sm opacity-70 hidden">
+      <div id="busuanzi_container" class="text-xs opacity-70 hidden">
         <div class="space-x-2">
           <span>Page Views: <span id="busuanzi_value_page_pv"></span></span>
           <span>|</span>