A 72-year-old woman with newly diagnosed non-valvular atrial fibrillation presents with palpitations. She has hypertension but no history of stroke, heart failure, diabetes, or vascular disease. Her blood pressure is 138/82 mm Hg and creatinine is 90 µmol/L. According to the Canadian CHADS-65 algorithm, which is the most appropriate antithrombotic strategy for stroke prevention?