Late-night fast food and 24-hour dining — once staples of American convenience — have shrunk dramatically in recent years, though some chains are beginning to expand overnight hours again. Across the country, fewer chains are keeping locations open overnight, a shift that began during the COVID-19 pandemic and never fully reversed.  Restaurant sales plunged 47% in April 2020 from a year earlier, forcing operators to cut hours and reduce costs, according to US Department of Agriculture (USDA) data cited…