A home inspection was most likely required at the time of sale. If the home inspector failed to discover this problem and/or it was not disclosed to you at time of purchase. Hire an attorney.
Basically, you'll need to throw away all the carpets.
If you don't have carpeting, but wood floors, there was probably some visible staining, this may be a problem if it was disclosed and you purchased because you'd get no compensation from anyone, even in court. However, the bottom line is that cat urine is basically one of the worst odors to rid from a dwelling. By the sounds of your description, you need some professional assistance both with legal privilege and cleaning.