Washington (AFP) – President Donald Trump, who is refusing to concede election defeat, injected new volatility Monday by firing his defense secretary, while President-elect Joe Biden made good on a promise to focus on leading the country out of the Covid-19 crisis.With construction already starting in central Washington for the January 20 inauguration ceremony, an awkward and potentially chaotic transition period is underway.Trump, in a move unprecedented for a US president, insists that the November 3 election was stolen from him. However, his lawyers have so far produced only flimsy evidence…