Yes, yes, fro-yo might be the season’s trendiest treat, but cupcakes continue to melt our heart. And why shouldn’t they? Cupcakes are delicious! Devotees should know that Courtney Forrester opens her fourth Sweet location at 11 School Street in Downtown Crossing today, right across from Borders. Bleary-eyed cube-dwellers in need of a frosting fix, rejoice!