Its rebirth has been announced many times before, but this time it’s looking serious: Fulton Mall and its Downtown Brooklyn environs are poised to boom. No less an authority than Danny Meyer has anointed 409 Fulton Street as the location for the borough’s first Shake Shack. (It’ll land just down the street from the borough’s first Panera Bread.) And even bigger chains have come calling: An Aéropostale just opened, and a Filene’s Basement and a 30,000-square-foot H&M are on the way. Farther east, the Albee Square Mall site will be rebranded the Dekalb Market this summer, with up to 40 food, clothing, and furniture vendors setting up shop in 160-square-foot shipping containers. (Eventually, the space will be converted into City Point, a mixed-use project with more than 50,000 square feet of stores.) Real estate is coming in just as fast, with more than 5,000 apartments added to the area since 2007.