For the millions of miles traveled by the space shuttle Endeavour it was the final stretch that mattered most to the region that rightfully calls itself the the birthplace of the shuttle program. From the deserts of Palmdale, where the orbiters were built, to the west San Fernando Valley, where engineers developed the mighty main engines, Southern California is the cradle of the technology that sent Endeavour and its predecessors into space. Last month, Endeavour made its final mission home to retire at the California Science Center.