A 22-year-old female presents with recurrent skin purpura and menorrhagia for 2 years. Physical exam: icteric sclera. Lab results: Hb 70g/L, WBC 5.6×10⁹/L, PLT 20×10⁹/L, reticulocytes 0.25, bleeding time 4 min, poor clot retraction. Coombs test (+), ultrasound shows mild splenomegaly. Bone marrow: erythroid hyperplasia (45%) with increased megakaryocytes (mostly immature/granular forms, few platelet-producing forms). The most likely diagnosis is: