KIM KARDASHIAN spotted the trend early, true to form. In 2021 the American reality-television star and her sister Khloé went bunker shopping. They tested a $200,000 facility made by a firm called Atlas Survival Shelters which provides 46 square metres (500 square feet) of safe space. Mark Zuckerberg, the billionaire founder of Meta, a social-media empire, is reportedly building a less cramped 450-square-metre facility under his ranch on a…