A 32-year-old woman presents to the emergency department with spontaneous bleeding from gums and multiple petechiae over her lower limbs for 3 days. She denies any recent trauma or drug intake. Vital signs are stable. Laboratory investigations reveal: Hemoglobin 10.2 g/dL, Platelet count 8,000/μL, PT 12 sec (control 12 sec), aPTT 32 sec (control 32 sec), Bleeding time 8 minutes (normal <5 min). Peripheral blood smear shows no abnormal cells. What is the most likely diagnosis?