A 55-year-old man presents to the emergency department with acute onset pleuritic chest pain and dyspnoea. He returned from a 10-hour flight 3 days ago. Vital signs: temperature 37.3°C, HR 110 beats/min, BP 130/80 mm Hg, RR 24/min, SpO₂ 91% on room air. D-dimer is elevated, and CT pulmonary angiography confirms a segmental pulmonary embolism. He is haemodynamically stable. What is the most appropriate disposition?