Employees of Bear Sterns have a reason to celebrate, after joining clients, honored guests including Gov. Pataki, and their chairman Jimmy Cayne for a night to remember. Just after dusk on a recent evening, they witnessed the lighting of the 7-story crown surrounding the company's new world headquarters. The feature is the first of its kind in New York and is comprised of a series of glass panels between 30 and 70 feet high. It illuminates the night sky with the aid of bulbs running more than a half-mile in length. And during the day with the aid of the sun it will do the same. Bear Sterns, founded in 1923, recently finished moving 4,200 employees into its new 1.2 million-square-foot facility at 383 Madison Ave.