The Kane Co.’s abrupt closure in December opened a door for another local company — and not just any door. The coveted White House moving contract now belongs to D.C.-based Proven Management LLC, a small moving firm that won the General Services Administration competition for the presidential transition after Kane and its affiliate, Lanham-based Office Movers Inc., shut down. The transition process, said Proven Management President and CEO Denita Conway, involves helping President Barack Obama…