As expected, thousands showed up at Gillette Stadium Friday to audition for “American Idol.’’ The show’s host, Ryan Seacrest, was there, but the early-morning rain kept him mostly indoors and out of view of the crowd. Several aspiring singers told us they were anxious but determined. Fifteen-year-old Sam Faherty of Pembroke hoped to catch the ear of judges with her own arrangement of the Macklemore and Ryan Lewis hit “Thrift Shop,’’ while Jarad Brockman, who lives in Needham, was auditioning for the second time. “I tried in Denver,’’ the Colorado native said, admitting he “got a little nervous’’ the first time. The 26-year-old dance instructor-turned-singer planned to sing “Walking in Memphis’’ by Marc Cohn.