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/asynckit/serial.js

@@ -0,0 +1,17 @@
+var serialOrdered = require('./serialOrdered.js');
+
+// Public API
+module.exports = serial;
+
+/**
+ * Runs iterator over provided array elements in series
+ *
+ * @param   {array|object} list - array or object (named list) to iterate over
+ * @param   {function} iterator - iterator to run
+ * @param   {function} callback - invoked when all elements processed
+ * @returns {function} - jobs terminator
+ */
+function serial(list, iterator, callback)
+{
+  return serialOrdered(list, iterator, null, callback);
+}