It really doesn't matter how well you clean, if the place smells like cat, or cat litter box, regardless of whether a guest has allergies, that's going to taint the guest's perception of whether the place is clean, unless they also happen to be cat people who are desensitized to the smell of a cat litter box.
That you would keep it in the living room is rather bizarre to me, but litter boxes have always grossed me out. Can you move it to a space the guests don't have access to, or some out-of the way spot?
I also have a cat and a dog, but they are primarily outside animals and there is no litter box. As far as guests who may be allergic to cats, some guests can be really clueless about being proactive and taking responsibility for their own health. And many guests simply don't thoroughly read the listing description- they read the first few lines, look at the photos and price, and book.
So you should have a photo of the cat in your photo gallery, because visual images are more likely to be mentally registered than just words.
What I do is have in my "other things to note" section that I have a dog and cat and to please not book my listing if they have allergies to animals or are scared of them. (I know many people are scared of dogs, but I didn't realize some are terrified of cats until I read of host's experiences here where they had cat-phobic guests). I also re-iterate that in my booking message to guests "So just checking that you read that I have a dog and a cat?" Depending on their answer, that also gives me an indication as to whether they actually read through all my info. And if they didn't notice that and have a issue with it, I've thereby given them an opportunity to cancel while they can still get a full refund.
@Scott1265