SAN FRANCISCO -- A pickup truck struck and killed a 35-year-old bicycle messenger today next to Alamo Square, San Francisco police said. The accident happened at 10:55 a.m. at Fulton and Steiner streets at the northeast corner of the square. The bicycle messenger was a San Francisco man whose name has not yet been released. The bicyclist was headed east on Fulton toward downtown in a bike lane when the pickup driver, headed north on Steiner, struck him in the intersection,