In his 18 years at Pinckney Community High School, Jim Darga, the principal, said, the homecoming queen had always been crowned at halftime of the school’s football game. Never before, though, had she had to be summoned from the team’s locker room. And that was just the beginning of Brianna Amat’s big night. If being named homecoming queen is a lifetime memory for a high school student, so, too, is kicking a winning field goal. For Amat, 18, they happened within an hour of each other.