The crowd at Dallas’s AT&T Stadium fell into a hush as Blake Shelton stopped strumming mid-song, his eyes locking onto a weathered sign held high in the front row: “I got into Stanford. You said we’d sing.” The arena held its breath as a young woman stepped up onto the stage — Lily Tran, once a foster child, now a full-scholarship student at Stanford University, one of the most prestigious institutions in America. At just 9 years old, Lily had met Blake at a backstage meet-and-greet…