A 2-year-old girl from coastal Tamil Nadu presents with her father reporting a 6-week history of progressive weakness, irritability, and recurrent respiratory infections. On examination, she has bleeding gums, poor wound healing, and petechial rash over her lower extremities. Her hemoglobin is 9.8 g/dL. Serum vitamin C level is 0.2 mg/dL (normal >0.6 mg/dL). Her diet consists mainly of boiled rice, lentils, and milk with no fresh fruits or vegetables. What is the most likely diagnosis?