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/axios/lib/platform/index.js

@@ -0,0 +1,7 @@
+import platform from './node/index.js';
+import * as utils from './common/utils.js';
+
+export default {
+  ...utils,
+  ...platform,
+};