A 70-year-old man with known COPD (FEV1 45% predicted) presents with increased breathlessness, productive cough with green sputum and wheeze over 3 days. His baseline therapy includes a LAMA/LABA inhaler. Observations: RR 22/min, SpO2 90% on air, temperature 37.8°C. Chest x-ray shows no new consolidation. What is the most appropriate next step in management?