NEW YORK — President Joe Biden praised NYC Mayor Eric Adams’ crimefighting agenda Thursday and unveiled a new federal initiative to stem the flow of illegal weapons from southern states that has contributed to a recent surge in violence in New York. Marking his first visit to the city since Adams’ inauguration, Biden gave his seal of approval to the mayor’s anti-crime push during a press conference at the NYPD’s downtown Manhattan headquarters, where they also received a classified briefing from the department’s joint gun violence task force. “I want to help every major city follow New York’s …