d of foresee- ability is not a 'sufficient benchmark' for exercising personal jurisdiction." Burger King, 471 U.S. at 474, 105 S.Ct. 2174 (quoting World—Wide Volkswagen, 444 U.S. at 295, 100 S.Ct. 559). In every case, there must be "some act by which the defendant purposefully avails itself of the privilege of co