A 48-year-old man from Delhi presents with a 6-week history of progressive cognitive decline, personality changes, and recent-onset focal seizures. His wife reports he has become withdrawn and irritable. MRI brain shows a large, infiltrative mass centered in the right temporal lobe with heterogeneous signal intensity, extensive peritumoral edema, and patchy areas of necrosis. Post-gadolinium imaging reveals irregular, incomplete ring enhancement. Perfusion MRI shows elevated relative cerebral blood volume (rCBV) within the enhancing portion. What is the most likely diagnosis?