A 32-year-old woman from rural Maharashtra presents with a 3-day history of severe epistaxis and gum bleeding. She has no prior bleeding tendency. On examination, she is pale with petechiae on her lower extremities. Her platelet count is 8,000/μL, PT is 14 seconds (control 12), aPTT is 38 seconds (control 32), and fibrinogen is 280 mg/dL. A bone marrow aspirate shows hypercellular marrow with increased megakaryocytes. What is the most likely diagnosis?