The way Jorge Posada sees it, the New York Yankees must add an ace to their rotation. That’s why he wants Johan Santana pitching in pinstripes next year. “We need a No. 1,” Posada said Thursday after the All-Star catcher finalized his new contract with the Yankees. “I would love to have him.” New York is involved in trade talks with the Minnesota Twins about their two-time Cy Young Award winner, who…