A 52-year-old man from Delhi presents to the neurology clinic with a 3-month history of severe, lancinating pain in the right cheek and upper jaw. The pain is triggered by chewing, touching the face, or cold wind, and lasts 10–30 seconds per episode. Neurological examination is normal; there is no sensory loss or motor weakness. MRI brain with contrast is unremarkable. What is the most likely diagnosis?