A 28-year-old woman from Kerala presents with a 5-day history of high fever (39.5°C), severe joint pain (especially wrists, ankles, and knees), and a maculopapular rash on the trunk and extremities. She also reports myalgia and headache. On examination, she has conjunctival injection without exudate, and joint swelling is noted. Laboratory investigations show thrombocytopenia (platelets 95,000/μL) and elevated transaminases (AST 120 U/L, ALT 95 U/L). A rapid NS1 antigen test is negative, but IgM antibodies against a mosquito-borne virus are positive. Which of the following is the most likely diagnosis?