A 32-year-old man from rural Odisha presents to the emergency department with a 5-day history of fever, chills, and headache. On examination, he is febrile (39.5°C), with mild jaundice and hepatosplenomegaly. Laboratory investigations reveal: Hb 9.2 g/dL, platelets 65,000/μL, creatinine 2.1 mg/dL, and bilirubin 3.8 mg/dL (predominantly indirect). Thick and thin blood smears show ring forms and Maurer's clefts. What is the most appropriate immediate management?