A 22-year-old male presents to the emergency department with a 16-hour history of periumbilical pain that migrated to the right lower quadrant. On examination, he has a temperature of 38.2°C, localized tenderness at McBurney's point, and a positive Rovsing's sign. His white blood cell count is 14,200/μL with left shift. Ultrasound shows a non-compressible, dilated appendix with appendicolith. What is the most appropriate next step in management?