TikTok is back on Apple and Google's US app stories after President Trump said the tech giants would not be fined if they reactivated it. They removed the hugely popular video-sharing app after a law came into effect on 19 January – the day before Mr Trump was inaugurated – requiring its Chinese owner ByteDance to sell up or face a ban. There were concerns that Beijing could use TikTok to spy on American users and the app, used by almost half of all Americans, briefly went dark. But the service was restored after Mr Trump said he would sign…