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/modern/QueryClientProvider.js

@@ -0,0 +1,36 @@
+"use client";
+
+// src/QueryClientProvider.tsx
+import * as React from "react";
+import { jsx } from "react/jsx-runtime";
+var QueryClientContext = React.createContext(
+  void 0
+);
+var useQueryClient = (queryClient) => {
+  const client = React.useContext(QueryClientContext);
+  if (queryClient) {
+    return queryClient;
+  }
+  if (!client) {
+    throw new Error("No QueryClient set, use QueryClientProvider to set one");
+  }
+  return client;
+};
+var QueryClientProvider = ({
+  client,
+  children
+}) => {
+  React.useEffect(() => {
+    client.mount();
+    return () => {
+      client.unmount();
+    };
+  }, [client]);
+  return /* @__PURE__ */ jsx(QueryClientContext.Provider, { value: client, children });
+};
+export {
+  QueryClientContext,
+  QueryClientProvider,
+  useQueryClient
+};
+//# sourceMappingURL=QueryClientProvider.js.map