President-elect Donald J. Trump said on Monday that he would nominate Harmeet K. Dhillon, a California lawyer who has long championed Mr. Trump in public, in court cases and on social media, to run the Justice Department’s Civil Rights Division. In declaring his choice on social media, Mr. Trump said Ms. Dhillon “has stood up consistently to protect our cherished civil liberties.” He praised her legal work targeting social media companies, restrictions on religious gatherings during the...