A 28-year-old woman with a 4-year history of Crohn's disease (ileocecal involvement, previously well-controlled on azathioprine) presents with a 2-week history of worsening abdominal pain, diarrhea (5–6 stools/day), and a palpable right lower quadrant mass. CT enterography shows a 4 cm segment of ileocecal stricturing with proximal bowel dilatation and no fistulas or abscess. She is afebrile, Hb 10.8 g/dL, CRP 2.1 mg/dL, and albumin 3.2 g/dL. What is the most appropriate next step in management?