A 38-year-old woman from rural Maharashtra presents with progressive fatigue, dyspnea on exertion, and palpitations for 6 months. She reports heavy menstrual bleeding since menarche. On examination: pallor, tachycardia (HR 102/min), and a systolic flow murmur. Laboratory findings: Hemoglobin 7.2 g/dL, MCV 62 fL, MCH 18 pg, RBC 5.8 × 10¹²/L, serum ferritin 8 ng/mL, serum iron 35 µg/dL, TIBC 420 µg/dL. Peripheral blood smear shows microcytic hypochromic RBCs with occasional target cells. What is the most likely diagnosis?