US President-elect Donald Trump was welcomed by arch-rival Joe Biden to the White House on Wednesday for a traditional transition meeting, a week after Trump and his Republican party swept to power in Washington in a stunning political comeback. In front of reporters and a roaring firing in the Oval Office, Biden greeted Trump with a handshake. During a brief on-camera exchange, both promised that the shift in power would be seamless. Biden, who leaves office on January 20, said there would be a “smooth transition” and told Trump that his administration would “do everything we can to make sure…