MIAMI — Before he was stabbed to death by his OnlyFans model girlfriend in Miami, Christian “Toby” Obumseli chronicled their arguments in a series of disturbing phone recordings that included racial slurs and her angrily screaming, berating and cursing him out in private and in public. The apparently secret recordings, now in evidence in the murder case against Courtney Clenney, offer a revealing window into their deeply toxic relationship — and could one day be presented to a jury to depict her as a domestic abuser who ultimately plunged a knife into the chest of her boyfriend inside their lu…