A 58-year-old man with diabetes mellitus type 2 presents to the emergency department with a 2-day history of fever (39.5°C), chills, and productive cough. He reports dysuria and frequency. On examination, he is tachypneic (RR 28/min), tachycardic (HR 118/min), and hypotensive (BP 88/54 mmHg). Skin is warm and flushed. Laboratory investigations show WBC 18,500/μL, lactate 4.2 mmol/L (normal <2), and creatinine 2.1 mg/dL (baseline 1.0). Blood and urine cultures are pending. Chest X-ray shows right lower lobe infiltrate. What is the most appropriate immediate management?