A 38-year-old woman from rural Maharashtra presents with a 3-month history of progressive fatigue, dyspnea on exertion, and recurrent oral ulcers. On examination, she is pale with petechiae over the lower limbs and hepatosplenomegaly. Laboratory investigations reveal: Hemoglobin 7.2 g/dL, WBC 2,100/μL, platelets 45,000/μL, reticulocyte count 0.8%, and normal B12 and folate levels. Bone marrow aspiration shows hypocellular marrow with 2% blasts. What is the most likely diagnosis?