Layla Welch planned to join Eden Prairie High School’s track and field team as a manager this spring. Instead, the 16-year-old became the first wheelchair racer in school history. By July, she had competed at the state meet and two national meets — using a secondhand chair that was not built for her. Natalie Wood, an Eden Prairie assistant track and field coach for horizontal jumps and sprints, organized a $9,000 GoFundMe campaign to help purcha…