S’no thank you. The Mamdani administration failed for hours to attract any emergency shovelers at one Queens garage Sunday — while planning to try to dig out New Yorkers with a fourth of the force the city used for its last mega-storm. Despite Mayor Zohran Mamdani’s widespread attempted promotion of the city’s public-fueled emergency shoveling program, a sign-up sheet at the Maspeth Sanitation garages was empty, city workers told The Post during a visit late Sunday morning. “I haven’t seen anybody sign up yet today. No, no one,” the employee said. There were also no signs of shovelers lining up...