President Sergio Mattarella went to Milan's Niguarda hospital on Monday to visit the young people being treated there after suffering injuries in the New Year's Eve bar fire at the Swiss resort of Crans-Montana.     The death toll from the disaster rose to 41 at the weekend after a Swiss teenager died of her injuries.     Six Italian teens were among the victims.     In addition to meeting in the injured young people, the head of State also spoke to some of their relatives and to doctors.