A 2-year-old girl from Delhi presents with hemolytic anemia, jaundice, and dark urine after eating fava beans. Laboratory tests show: - Hemoglobin: 8.5 g/dL (baseline 11 g/dL) - Reticulocyte count: 8% (elevated) - Serum bilirubin: 4.2 mg/dL (conjugated 0.3 mg/dL) - Peripheral blood smear: Heinz bodies, schistocytes - RBC glucose-6-phosphatase dehydrogenase (G6PD) activity: 5% of normal The child is hemodynamically stable. What is the most appropriate immediate next step?