Eight years ago, Samantha Bowers landed a residency at the Cotton Club. The place wasn’t quite the jazz institution it had been nearly a century ago. Her gig consisted of singing just a couple of jazz standards on a Friday night. She had to trek two hours from Brooklyn to Harlem in a black dress and heels every week. But it was a job. And, as it turns out, it was a doorway that led Bowers to the life of her dreams.