A 72-year-old man with a history of ischaemic heart disease and type 2 diabetes presents with a 3-day history of productive cough, fever (38.5°C), and shortness of breath. His respiratory rate is 24/min, heart rate 110/min, BP 130/80 mmHg, and oxygen saturation 93% on air. Chest auscultation reveals crackles in the left lower zone. His CURB-65 score is calculated as 1 (age ≥65). What is the most appropriate initial management setting according to NICE guidelines?