A 62-year-old woman with known diverticular disease presents with a 2-day history of left iliac fossa pain and fever (38.5°C). She reports no rectal bleeding. On examination, she is tender in the left iliac fossa, with localised guarding. Blood tests show WCC 14 x10^9/L and CRP 120 mg/L. According to NICE NG147, what is the most appropriate management strategy for this likely uncomplicated acute diverticulitis?