A 52-year-old man from Delhi presents with progressive fatigue, mild dyspnea, and bone pain for 3 months. He has a 10-year history of rheumatoid arthritis treated with NSAIDs and methotrexate. On examination: pallor, no lymphadenopathy, no hepatosplenomegaly. Laboratory findings: Hemoglobin 8.9 g/dL, MCV 78 fL, serum creatinine 2.1 mg/dL (eGFR 28 mL/min), serum iron 92 µg/dL, TIBC 280 µg/dL, serum ferritin 180 ng/mL, reticulocyte count 0.8%, bone marrow shows normocellular marrow with adequate iron stores. What is the most likely diagnosis?