Shenzhen may be the world's largest electronics market, but when the computer buyers head home at 10pm every night, the beauty industry takes over 1,400 stalls in the vast Mingtong mall.    Here, workers will be up until 2am at least to meet wholesale demand for lipsticks, face creams and more. According to official data from the China government, cosmetics sales rose 5.9% to more than $39 billion for the 10 months ended in October. That's a quite a contrast with overall retail...