NEW YORK — The New York City government’s ethics watchdog ordered former Mayor Bill de Blasio on Thursday to cough up nearly $500,000 for misusing his personal police detail during his failed 2020 presidential campaign — the largest fine ever levied by the agency. The extraordinary punishment from the city Conflicts of Interest Board — which de Blasio’s attorney immediately vowed to challenge in court — caps off a years-long probe into the ex-mayor’s decision to have his NYPD detail tag along with him on 31 out-of-state campaign trips in 2019 as part of his long-shot bid for the Democratic Par...