NEW YORK — SA will celebrate the official launch of the Fashion Center Business Improvement District Thursday at a ceremony at the plaza sidewalk in front of 1411 Broadway. Bill Blass, Nicole Miller, Michael Kors, Cynthia Steffe, Christian Francis Roth and Cathy Hardwick have created special items incorporating the FCBID’s button logo — a large black button with thread holes forming the letter F for fashion — which will be unveiled at the event.