Add dark mode UI and update components

ui/styles.css

@@ -20,6 +20,23 @@
     --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
 }
 
+/* Dark mode theme */
+[data-theme="dark"] {
+    --primary-color: #3b82f6;
+    --primary-hover: #2563eb;
+    --secondary-color: #9ca3af;
+    --success-color: #10b981;
+    --danger-color: #ef4444;
+    --warning-color: #f59e0b;
+    --bg-color: #1a1a1a;
+    --surface-color: #2d2d2d;
+    --border-color: #404040;
+    --text-primary: #f3f4f6;
+    --text-secondary: #d1d5db;
+    --shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
+    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.3);
+}
+
 body {
     font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
     background-color: var(--bg-color);
@@ -163,6 +180,16 @@ main {
     white-space: nowrap;
 }
 
+.tree-nested {
+    display: block;
+}
+
+.tree-item-toggle {
+    display: inline-block;
+    min-width: 1rem;
+    text-align: center;
+}
+
 .loading {
     padding: 2rem 1rem;
     text-align: center;