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/nth.js

@@ -0,0 +1,29 @@
+var baseNth = require('./_baseNth'),
+    toInteger = require('./toInteger');
+
+/**
+ * Gets the element at index `n` of `array`. If `n` is negative, the nth
+ * element from the end is returned.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.11.0
+ * @category Array
+ * @param {Array} array The array to query.
+ * @param {number} [n=0] The index of the element to return.
+ * @returns {*} Returns the nth element of `array`.
+ * @example
+ *
+ * var array = ['a', 'b', 'c', 'd'];
+ *
+ * _.nth(array, 1);
+ * // => 'b'
+ *
+ * _.nth(array, -2);
+ * // => 'c';
+ */
+function nth(array, n) {
+  return (array && array.length) ? baseNth(array, toInteger(n)) : undefined;
+}
+
+module.exports = nth;