A 6-year-old girl from Mumbai with newly diagnosed B-cell acute lymphoblastic leukemia (ALL) has completed 4 weeks of induction chemotherapy. Bone marrow aspirate shows <5% blasts (complete remission achieved). However, she now presents with severe mucositis, oral candidiasis, and a fever of 39.2°C. Her absolute neutrophil count (ANC) is 200/μL. What is the most appropriate next step in management?