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/agent-base/dist/helpers.d.ts

@@ -0,0 +1,15 @@
+/// <reference types="node" />
+/// <reference types="node" />
+/// <reference types="node" />
+/// <reference types="node" />
+/// <reference types="node" />
+import * as http from 'http';
+import * as https from 'https';
+import type { Readable } from 'stream';
+export type ThenableRequest = http.ClientRequest & {
+    then: Promise<http.IncomingMessage>['then'];
+};
+export declare function toBuffer(stream: Readable): Promise<Buffer>;
+export declare function json(stream: Readable): Promise<any>;
+export declare function req(url: string | URL, opts?: https.RequestOptions): ThenableRequest;
+//# sourceMappingURL=helpers.d.ts.map