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/@tanstack/react-query/build/legacy/useIsFetching.js

@@ -0,0 +1,22 @@
+"use client";
+
+// src/useIsFetching.ts
+import * as React from "react";
+import { notifyManager } from "@tanstack/query-core";
+import { useQueryClient } from "./QueryClientProvider.js";
+function useIsFetching(filters, queryClient) {
+  const client = useQueryClient(queryClient);
+  const queryCache = client.getQueryCache();
+  return React.useSyncExternalStore(
+    React.useCallback(
+      (onStoreChange) => queryCache.subscribe(notifyManager.batchCalls(onStoreChange)),
+      [queryCache]
+    ),
+    () => client.isFetching(filters),
+    () => client.isFetching(filters)
+  );
+}
+export {
+  useIsFetching
+};
+//# sourceMappingURL=useIsFetching.js.map