A 38-year-old woman presents to the emergency department with severe headache, profuse sweating, and palpitations lasting 2 hours. Blood pressure is 185/110 mmHg, heart rate 112/min, and she appears anxious. She reports episodic symptoms over the past 6 months with sudden onset of chest tightness and tremor. Serum glucose is 180 mg/dL despite no prior diabetes. 24-hour urine metanephrines are markedly elevated at 1200 µg (normal <400). CT abdomen shows a 3.5 cm left adrenal mass. Which is the most appropriate next step in management?