A 32-year-old man is brought to the emergency department following a motor vehicle collision. He was the restrained driver of a car that struck a tree at high speed. On arrival, his blood pressure is 95/62 mmHg, heart rate 118 bpm, respiratory rate 24/min, and GCS 15. Abdominal examination reveals a seatbelt sign across the lower abdomen with mild tenderness. FAST examination shows free fluid in the pelvis. His hemoglobin is 10.2 g/dL (baseline unknown). After 2 liters of crystalloid resuscitation, his BP improves to 105/68 mmHg and HR decreases to 105 bpm. Repeat FAST shows no increase in free fluid. What is the most appropriate next step in management?