Audrey's Pizza, a Bozeman institution known for its cracker-thin crust and hand-drawn boxes, is preparing to close its doors later this month after nearly nine decades of serving the Gallatin Valley.The pizza shop's origins trace back to the 1940s. During World War II, flour rations forced the original owners to get creative, using whey instead of flour a workaround that accidentally created the iconic cracker-thin crust the restaurant is still …