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/@nodelib/fs.walk/out/providers/sync.d.ts

@@ -0,0 +1,10 @@
+import SyncReader from '../readers/sync';
+import type Settings from '../settings';
+import type { Entry } from '../types';
+export default class SyncProvider {
+    private readonly _root;
+    private readonly _settings;
+    protected readonly _reader: SyncReader;
+    constructor(_root: string, _settings: Settings);
+    read(): Entry[];
+}