A 3-day-old male neonate born to non-consanguineous parents presents with cyanosis noticed since birth. On examination, he is tachypneic (RR 65/min), has clubbing of fingers, and a single loud S2. Chest X-ray shows an 'egg-on-string' appearance with decreased pulmonary vascularity. Echocardiography reveals anterior aorta overriding a ventricular septal defect with right ventricular outflow tract obstruction. What is the most likely diagnosis?