There aren’t many professional sports franchises that get a birthday party thrown by fans. On the Chicago Fire’s 15th anniversary Monday night, the staff, current players and former players celebrated with fans who paid $97 to attend a party at the Chicago History Museum, and about 500 people attended the event organized by the Fire’s supporters groups. Proceeds from the admission charge and a silent auction benefited the Fire’s charitable foundation. “It’s really remarkable for that to happen,” said Peter Wilt, the Fire’s first general manager. “A team loved so much by ...