A 16-year-old boy presents to the ENT clinic with a 6-month history of progressive unilateral nasal obstruction and recurrent epistaxis. His mother reports he has been a mouth-breather and complains of difficulty during sports. On nasal endoscopy, a smooth, glistening, reddish mass is seen in the nasopharynx, extending into the nasal cavity. CT scan shows a well-defined mass with heterogeneous enhancement and bowing of the posterior maxillary wall. Angiography reveals a highly vascular lesion with feeding vessels from the maxillary artery. What is the most likely diagnosis?