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/stubObject.js

@@ -0,0 +1,23 @@
+/**
+ * This method returns a new empty object.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.13.0
+ * @category Util
+ * @returns {Object} Returns the new empty object.
+ * @example
+ *
+ * var objects = _.times(2, _.stubObject);
+ *
+ * console.log(objects);
+ * // => [{}, {}]
+ *
+ * console.log(objects[0] === objects[1]);
+ * // => false
+ */
+function stubObject() {
+  return {};
+}
+
+module.exports = stubObject;