A 5-year-old girl from Delhi presents with a 3-day history of fever, cough, and rapid breathing. On examination, she is irritable, has a respiratory rate of 52/min, intercostal retractions, and a capillary refill time of 3 seconds. Pulse is 140/min, blood pressure is 85/50 mmHg, and oxygen saturation is 88% on room air. Chest auscultation reveals bilateral crackles. A rapid diagnostic test confirms influenza A. What is the most appropriate immediate next step?