A 18-month-old boy from rural Rajasthan presents with his mother who reports poor feeding, irritability, and constipation for the past 3 weeks. On examination, he appears pale and lethargic. His hemoglobin is 7.2 g/dL. Peripheral blood smear shows microcytic hypochromic anemia with target cells. Serum iron is low at 25 µg/dL (normal 50–150), and serum ferritin is 8 ng/mL. His diet consists mainly of milk and rice with minimal meat or fortified cereals. What is the most likely diagnosis?