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/_stackGet.js

@@ -0,0 +1,14 @@
+/**
+ * Gets the stack value for `key`.
+ *
+ * @private
+ * @name get
+ * @memberOf Stack
+ * @param {string} key The key of the value to get.
+ * @returns {*} Returns the entry value.
+ */
+function stackGet(key) {
+  return this.__data__.get(key);
+}
+
+module.exports = stackGet;