A 32-year-old man from rural Maharashtra presents with jaundice, dark urine, and clay-coloured stools for 10 days. He reports consuming contaminated water 6 weeks ago. On examination, he is afebrile with mild hepatomegaly and no ascites. Laboratory investigations show: total bilirubin 8.2 mg/dL, ALT 2400 U/L, AST 1800 U/L, ALP 180 U/L, albumin 3.8 g/dL, INR 1.1. Anti-HAV IgM is positive; anti-HEV IgM is negative. What is the most likely diagnosis?