NEW YORK — President Joe Biden is expected to announce a nationwide crackdown on so-called “ghost guns” during his Thursday visit to New York City, where the untraceable weapons have proliferated in the past two years, according to administration officials. The homemade weapons, which typically aren’t subject to background checks and lack traceable serial numbers, have contributed to a spike in gun violence during the pandemic, especially in large cities like New York, Los Angeles and Chicago. While in the city for a meeting with Mayor Eric Adams and other officials on Thursday afternoon, Bide…