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/isObject.js

@@ -0,0 +1,31 @@
+/**
+ * Checks if `value` is the
+ * [language type](http://www.ecma-international.org/ecma-262/7.0/#sec-ecmascript-language-types)
+ * of `Object`. (e.g. arrays, functions, objects, regexes, `new Number(0)`, and `new String('')`)
+ *
+ * @static
+ * @memberOf _
+ * @since 0.1.0
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is an object, else `false`.
+ * @example
+ *
+ * _.isObject({});
+ * // => true
+ *
+ * _.isObject([1, 2, 3]);
+ * // => true
+ *
+ * _.isObject(_.noop);
+ * // => true
+ *
+ * _.isObject(null);
+ * // => false
+ */
+function isObject(value) {
+  var type = typeof value;
+  return value != null && (type == 'object' || type == 'function');
+}
+
+module.exports = isObject;