A 42-year-old woman from Mumbai presents with sudden onset left lower quadrant pain and fever for 8 hours. On examination, she has localized peritoneal signs in the left iliac fossa. CT abdomen shows a perforated diverticulum with a small localized abscess (3 cm) confined to the pelvis, minimal free fluid, and no evidence of generalized peritonitis. Her vitals are stable: BP 118/76 mmHg, HR 92/min, Temperature 38.2°C. She is alert and cooperative. What is the most appropriate next step in management?