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/set-function-length/index.d.ts

@@ -0,0 +1,7 @@
+declare namespace setFunctionLength {
+    type Func = (...args: unknown[]) => unknown;
+}
+
+declare function setFunctionLength<T extends setFunctionLength.Func = setFunctionLength.Func>(fn: T, length: number, loose?: boolean): T;
+
+export = setFunctionLength;