Panicked investors scrambled desperately yesterday to determine whether their life savings had been wiped out after a Wall Street legend allegedly admitted blowing as much as $50 billion in what is emerging as the largest Ponzi scheme in history. Among several big-name investors who trusted former Nasdaq Chairman Bernard L. Madoff with their cash were New York Mets owners Fred Wilpon and Saul Katz, who may have lost as much as $500 million in the scheme, sources said. New Jersey Sen. Frank Lautenberg also confirmed he had invested money from his charitable organization through the 70-year-old Madoff's company, though he...