A 52-year-old woman with no significant past medical history presents with a 4-day history of cough, fever (39.2°C), pleuritic chest pain, and dyspnea. She lives in a community setting and has not been hospitalized recently. On examination: respiratory rate 24/min, SpO₂ 92% on room air, dullness to percussion and decreased breath sounds at the right base. Chest X-ray shows a right lower lobe consolidation with a small parapneumonic effusion. Blood cultures are pending. Sputum culture grows Streptococcus pneumoniae (penicillin-susceptible). What is the most appropriate antibiotic therapy?