A 3-year-old boy from South India presents with jaundice, pallor, and hepatosplenomegaly. His mother reports recurrent episodes of dark urine and abdominal pain over the past 6 months. On examination, he is icteric with a palpable spleen 4 cm below the costal margin. Laboratory investigations show: Hemoglobin 7.2 g/dL, reticulocyte count 12%, indirect bilirubin 4.8 mg/dL, direct bilirubin 0.6 mg/dL, LDH 680 U/L, haptoglobin <10 mg/dL. Peripheral blood smear reveals spherocytes and polychromasia. Osmotic fragility test is positive. What is the most likely diagnosis?