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/@testing-library/jest-dom/dist/vitest.mjs

@@ -0,0 +1,13 @@
+import { expect } from 'vitest';
+import { e as extensions } from './matchers-35e4d3bd.mjs';
+import 'redent';
+import '@adobe/css-tools';
+import 'dom-accessibility-api';
+import 'aria-query';
+import 'picocolors';
+import 'css.escape';
+
+/* istanbul ignore file */
+
+
+expect.extend(extensions);