If you’re not being sarcastic, why limit yourself to only one thing? If you’re working on some amazing UI with tons of CSS animations and a full audiovisual experience, and it takes intimate knowledge of everything frontend, I guess it would make sense. But if you’re just making internal CRUD apps, I don’t see a reason why a given domain is special enough to have its own job title.
Maybe the word “audit” is incorrect? If they didn’t provide you any guidelines, I’d definitely recommend asking. But it’s possible they’re just looking for your perspective on best practices and possible improvement ideas, more like a general code review.