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/lodash/_setToString.js

@@ -0,0 +1,14 @@
+var baseSetToString = require('./_baseSetToString'),
+    shortOut = require('./_shortOut');
+
+/**
+ * Sets the `toString` method of `func` to return `string`.
+ *
+ * @private
+ * @param {Function} func The function to modify.
+ * @param {Function} string The `toString` result.
+ * @returns {Function} Returns `func`.
+ */
+var setToString = shortOut(baseSetToString);
+
+module.exports = setToString;