The deadliest residential fire to hit New York City in at least a quarter century swept through a Bronx apartment building Thursday on one of the coldest nights this winter, killing 12 people and leaving four more fighting for their lives, city officials said. The blaze broke out on the first floor of a five-story building just before 7 p.m. and quickly ripped through the roughly century-old structure, which stands in a row of similar apartment buildings a block from the grounds of the Bronx Zoo. Tenants of the building, a mix of native New Yorkers and Latino and African immigrants, scrambled down fire escapes. But the flames moved so fast, spreading through every floor of the building within minutes, that many never made it out of their apartments.