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/es-object-atoms/isObject.js

@@ -0,0 +1,6 @@
+'use strict';
+
+/** @type {import('./isObject')} */
+module.exports = function isObject(x) {
+	return !!x && (typeof x === 'function' || typeof x === 'object');
+};