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/readers/common.d.ts

@@ -0,0 +1,7 @@
+import type { FilterFunction } from '../settings';
+import type Settings from '../settings';
+import type { Errno } from '../types';
+export declare function isFatalError(settings: Settings, error: Errno): boolean;
+export declare function isAppliedFilter<T>(filter: FilterFunction<T> | null, value: T): boolean;
+export declare function replacePathSegmentSeparator(filepath: string, separator: string): string;
+export declare function joinPathSegments(a: string, b: string, separator: string): string;