VATICAN CITY — Declaring that he lacks the strength to do his job, Pope Benedict XVI announced Monday he will resign Feb. 28 — becoming the first pontiff to step down in 600 years. His decision sets the stage for a mid-March conclave to elect a new leader for a Roman Catholic Church in deep turmoil. The 85-year-old pope dropped the bombshell in Latin during a meeting of Vatican cardinals, surprising even his closest collaborators even though he had made clear previously that he would step down if he became too old or infirm to carry on. Benedict called his …