For fans, players and political leaders who celebrated the Red Sox's World Series title with cries of "Boston Strong," the championship provided a jubilant finish to a season that was shadowed nearly from the start by the April bombings at the Boston Marathon. The success of the Red Sox, who finished last in their division only a year ago, became a welcome surprise and eventually a symbol of resilience for a city recovering from the twin bombings that killed three people and wounded more than 260.