Photo: married to potatoesIt's after dark in Manhattan, and the Upper West Side neighborhood of Morningside Heights is shutting down. The bagel shops and gourmet groceries, the restaurants and delicatessens, are closed or closing for the night, lights dimmed, iron gates shuttered over storefronts. On the sidewalks, black and translucent trash bags pile up. They are full of day-old salads, fruits, vegetables, bread, premade sandwiches, coffee grounds, receipts, and milk cartons. At 10 p.m., Annie Deng waits in the entrance of a Duane Reade on 110th Street. Her foldable hand cart, the kind used by older women across the city …