A 28-year-old woman from rural Maharashtra presents with a 3-day history of severe epistaxis and gum bleeding. She reports easy bruising for the past 2 weeks and denies any recent trauma or medication use. On examination, she has petechiae on her lower extremities and oral mucosa. Laboratory findings show: Hemoglobin 9.2 g/dL, WBC 6,500/μL, platelets 8,000/μL, PT 12 s (normal), aPTT 32 s (normal), bleeding time 8 min (prolonged). Bone marrow examination shows normocellular marrow with increased megakaryocytes. What is the most likely diagnosis?