Replace sidebar menu with collapsible category tree showing items

public/js/app.js

@@ -2,6 +2,22 @@ document.addEventListener('DOMContentLoaded', function() {
     const mainContent = document.getElementById('main-content');
     const appName = document.querySelector('.navbar-brand').textContent;
 
+    // Global function for editing item from tree
+    window.editItem = function(id) {
+        // Create a mock button to reuse handleEditItem
+        const mockBtn = { getAttribute: (attr) => attr === 'data-id' ? id : null };
+        handleEditItem.call(mockBtn);
+    };
+
+    // Function to toggle category children
+    window.toggleCategory = function(span) {
+        const li = span.parentElement;
+        const ul = li.querySelector('ul'); // First ul is children
+        if (ul) {
+            ul.style.display = ul.style.display === 'none' ? 'block' : 'none';
+        }
+    };
+
     // --- Helper Functions ---
     function setPageTitle(title) {
         document.title = `${appName} - ${title}`;