A 52-year-old woman with rheumatoid arthritis has been on naproxen 500 mg twice daily for 3 years. She now presents with epigastric pain, nausea, and dark tarry stools for 2 days. Upper endoscopy reveals a 1.5 cm gastric ulcer with active bleeding. She has no history of Helicobacter pylori infection (eradicated 5 years ago). Her hemoglobin is 8.2 g/dL (baseline 12 g/dL). After endoscopic hemostasis, which of the following is the most appropriate next step in her long-term management to prevent ulcer recurrence?