CAPE CANAVERAL, Fla. (AP) — Space shuttle Endeavour and its six astronauts closed out the last major construction mission at the International Space Station with a smooth landing in darkness that struck many as bittersweet.Only one flight remains for Endeavour, the baby of the shuttle fleet. Overall, just four missions remain.”We’ll go into it with our heads held high,” launch director Mike Leinbach said early Monday, a few hours after Endeavour landed in Florida. “A little bit sad note, but a great ending to a great mission.”