235 S. Old Woodward Ave., Birmingham, Mich.Take a step into Birmingham's tony downtown shopping district, and you'd have a hard time believing all the stories about Detroit's urban devastation and blue-collar denizens. The community's tree-lined streets are filled with upscale doggie bakeries, five-star eateries, and retailers with designer duds fresh from Fashion Week. With its sleek, modern mentality, Marcy Feldman's Heartwear Designs fits nicely into the nabe's rarefied atmosphere.Basement BeginningsMarcy Feldman graduated from the University of Michigan with a teaching degree and no job prospects. It was 1970, and the only work she could find was for Motif Manufacturing, a Detroit jewelry maker. "Normally, they hired the physically disabled. My disability was I was a woman," she says. But that one-year stint gave her a crash course in the business. "I started making jewelry in my bas