feat(frontend): add API client, layout, and routing

- Create Axios-based API client with sources, jobs, and dashboard endpoints
- Add responsive Layout component with navigation sidebar
- Set up React Router with Dashboard, Backups, and Settings routes
- Configure TanStack Query provider with default options
- Use lucide-react for navigation icons

frontend/node_modules/css-tree/lib/syntax/atrule/index.js

@@ -0,0 +1,15 @@
+import fontFace from './font-face.js';
+import importAtrule from './import.js';
+import media from './media.js';
+import nest from './nest.js';
+import page from './page.js';
+import supports from './supports.js';
+
+export default {
+    'font-face': fontFace,
+    'import': importAtrule,
+    media,
+    nest,
+    page,
+    supports
+};