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/vitest/dist/snapshot.d.ts

@@ -0,0 +1,9 @@
+import { NodeSnapshotEnvironment } from '@vitest/snapshot/environment';
+export { SnapshotEnvironment } from '@vitest/snapshot/environment';
+
+declare class VitestNodeSnapshotEnvironment extends NodeSnapshotEnvironment {
+    getHeader(): string;
+    resolvePath(filepath: string): Promise<string>;
+}
+
+export { VitestNodeSnapshotEnvironment as VitestSnapshotEnvironment };