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/stubFalse.js

@@ -0,0 +1,18 @@
+/**
+ * This method returns `false`.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.13.0
+ * @category Util
+ * @returns {boolean} Returns `false`.
+ * @example
+ *
+ * _.times(2, _.stubFalse);
+ * // => [false, false]
+ */
+function stubFalse() {
+  return false;
+}
+
+module.exports = stubFalse;