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/useMutation.js

@@ -0,0 +1,45 @@
+"use client";
+
+// src/useMutation.ts
+import * as React from "react";
+import {
+  MutationObserver,
+  noop,
+  notifyManager,
+  shouldThrowError
+} from "@tanstack/query-core";
+import { useQueryClient } from "./QueryClientProvider.js";
+function useMutation(options, queryClient) {
+  const client = useQueryClient(queryClient);
+  const [observer] = React.useState(
+    () => new MutationObserver(
+      client,
+      options
+    )
+  );
+  React.useEffect(() => {
+    observer.setOptions(options);
+  }, [observer, options]);
+  const result = React.useSyncExternalStore(
+    React.useCallback(
+      (onStoreChange) => observer.subscribe(notifyManager.batchCalls(onStoreChange)),
+      [observer]
+    ),
+    () => observer.getCurrentResult(),
+    () => observer.getCurrentResult()
+  );
+  const mutate = React.useCallback(
+    (variables, mutateOptions) => {
+      observer.mutate(variables, mutateOptions).catch(noop);
+    },
+    [observer]
+  );
+  if (result.error && shouldThrowError(observer.options.throwOnError, [result.error])) {
+    throw result.error;
+  }
+  return { ...result, mutate, mutateAsync: result.mutate };
+}
+export {
+  useMutation
+};
+//# sourceMappingURL=useMutation.js.map