A flurry of activity has returned to 360 Smith Street/ 131 Second Place, where a 48-unit, 70-foot residential building atop the Carroll Gardens stop on the F train will one day rise. The project, called Oliver House for developer William Stein’s father, hit a snag when the area was rezoned, but a city panel determined in late 2008 that a substantialenough percentage of the building’s foundation had been poured to allow work to continue — despite the zoning change, that now only permits building’s 55 feet tall. The developer’s lawyer claimed that work costing in excess of $3 million has already been performed at the site, justifying the continuation of the project.