feat: app icon button round

pages/admin/mail-log/view(default).phtml

@@ -23,7 +23,7 @@ $statusBadge = $status->badgeVariant();
     ?>
     <div class="app-details-titlebar">
       <h1>
-        <a href="admin/mail-log" title="<?php e(t('Back')); ?>"><i class="bi bi-arrow-left"></i></a>
+        <a href="admin/mail-log" title="<?php e(t('Back')); ?>" class="app-icon-button"><i class="bi bi-arrow-left"></i></a>
         <?php e(t('View mail log')); ?>
       </h1>
     </div>