There are few Swedes cooler than Ann-Sofie Back. The designer’s eponymous cult-favourite brand upended the notion of Scandi minimalism, embracing upcycling and so-called ugliness long before it was the norm. Now, with her hair-raising interiors collection Gnilmyd Kcab, co-founded with Mattias Dymling, she’s poised to shake up a whole new industry