LOS ANGELES — A California man has been charged with shipping weapons and ammunition to North Korea and told investigators they were to be used for a surprise attack on South Korea, authorities said Tuesday. Shenghua Wen came to the U.S. from China on a student visa more than a decade ago after meeting with North Korean officials who instructed him to procure goods for the North Korean government, according to the U.S. Attorney’s office in Los Angeles. Wen, 41, was arrested at his home in