Congressional investigators probing the Jan. 6 insurgency have seized the phone of a lawyer who advised former President Donald Trump on his efforts to overturn the results of the 2020 election, according to court documents. John Eastman, a California law professor, drew up and promoted a plan to justify having Vice President Mike Pence delay or block the Electoral College’s certification that would put the winner, Joe Biden, in the White House. Eastman also advised Trump to create purported slates of electors backing Trump in key swing states that Biden won. Federal agents armed with a search…