Integrate Lucide icons and replace inline SVGs

Add Lucide icon library and switch many inline SVGs to programmatically generated Lucide icons for consistent styling and reuse. Adds frontend/vendor/lucide.min.js and includes it in index.html; adds helper functions (escapeSvgAttr, svgAttrs, lucideIcon) in app.js and replaces numerous hard-coded SVG strings with Lucide-generated icons and CSS utility classes. Update components.css with .gd-lucide-icon, color helpers for folder/file icons, and remove a global stroke-width override so icon strokeWidth can be controlled per icon. Small accessibility and UI tweaks: use aria-label/title on several buttons and swap icons in modals, menus and toolbars. Also updates package.json/package-lock.json (dependency adjustments).

frontend/css/components.css

@@ -105,6 +105,20 @@
   display: none !important;
 }
 
+.gd-lucide-icon {
+  display: inline-block;
+  flex-shrink: 0;
+  vertical-align: -0.15em;
+}
+
+.gd-folder-icon {
+  color: #54aeff;
+}
+
+.gd-file-icon {
+  color: #848d97;
+}
+
 .accent {
   color: var(--accent);
 }
@@ -1009,7 +1023,6 @@
   height: 44px;
   fill: none;
   stroke: currentColor;
-  stroke-width: 4;
   stroke-linecap: round;
   stroke-linejoin: round;
 }