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).

package-lock.json

@@ -7,6 +7,9 @@
     "": {
       "name": "gitpub-desktop",
       "version": "0.1.0",
+      "dependencies": {
+        "lucide": "^1.14.0"
+      },
       "devDependencies": {
         "@tauri-apps/cli": "^2"
       }
@@ -227,6 +230,12 @@
       "engines": {
         "node": ">= 10"
       }
+    },
+    "node_modules/lucide": {
+      "version": "1.14.0",
+      "resolved": "https://registry.npmjs.org/lucide/-/lucide-1.14.0.tgz",
+      "integrity": "sha512-IoRC3lHwemJWvsXKcHK90hkgY4h1HGztBL63w2XwFtIu8gFDPp4/kiuqVtlN3vaM9bxsLQ4ZUBJfGsbKFaB2IA==",
+      "license": "ISC"
     }
   }
 }