By Jonathan Stempel NEW YORK (Reuters) – New York’s attorney general on Thursday sued Celsius Network founder Alex Mashinsky, claiming he defrauded investors out of billions of dollars in digital currency by concealing the failing health of his now-bankrupt cryptocurrency lending platform. Mashinsky fraudulently promoted Celsius as a safe alternative to banks, while concealing that it was losing hundreds of millions of dollars in risky investments, according to a complaint filed by the attorney general, Letitia James. The civil lawsuit filed in a New York state court in Manhattan seeks to ban …