A 38-year-old woman with acute promyelocytic leukemia (APL) presents to the emergency department with spontaneous bleeding from gums, epistaxis, and petechiae. Laboratory investigations reveal PT 18 s (control 12 s), aPTT 45 s (control 28 s), fibrinogen 85 mg/dL (normal 200–400), D-dimer >5000 ng/mL, and platelet count 35,000/μL. Peripheral blood smear shows abnormal promyelocytes with abundant Auer rods. What is the most appropriate immediate management?