feat: Enhance sidebar navigation with dropdowns and refactor breadcrumb structure

templates/checkpoints.html

@@ -31,6 +31,7 @@
 {% block content %}
     {% include 'components/controls.html' %}
     {% include 'components/duplicates_banner.html' %}
+    {% include 'components/folder_sidebar.html' %}
     
     <!-- Checkpoint cards container -->
     <div class="card-grid" id="modelGrid">
@@ -38,6 +39,10 @@
     </div>
 {% endblock %}
 
+{% block overlay %}
+<div class="bulk-mode-overlay"></div>
+{% endblock %}
+
 {% block main_script %}
 <script type="module" src="/loras_static/js/checkpoints.js"></script>
 {% endblock %}