ANNA Wintour was courtside at the Garden last night, but not to see the woeful Knicks. The Vogue editrix was a guest of Cleveland Cavaliers superstar LeBron James after dining with him the night before at the Waverly Inn. Her boyfriend, Shelby Bryan, was there as well, plus James’ business partner, Maverick Carter. Wintour, who fa mously befriended tennis champ Roger Federer, hasn’t switched sports. But she’ll have James on the April cover of Vogue with Gisele Bun dchen for the annual “shape issue.” Sources say James re vealed over dinner that he’s a huge fan of Ralph Lauren and wears a brand-new pair of sneakers for every game.