A 77-year-old woman is referred to the memory clinic with an 18-month history of progressive personality change, disinhibition, and loss of social awareness. Her husband reports she has been making inappropriate comments to strangers, has become apathetic about personal hygiene, and has developed a compulsive sweet tooth. Her memory is relatively preserved. MoCA is 23/30 with impairment in executive function tasks. MRI shows frontal and temporal lobe atrophy. What is the MOST likely diagnosis?