Shenzhen’s urban villagers have quietly amassed a combined fortune of more than $30 billion in ways that escape most outsiders. Villages like Huanggang sit on what has become some of the most expensive real estate anywhere in the world. But as millions of people face uncertain times as they flock to China’s Silicon Valley in search of better lives, resentment is building. Allen Wan reports from Shenzhen and Stella Ko in Hong Kong.