Ian Garfinkel is a true history buff. But then, he'd almost have to be - having taken on the challenge of running a 150-year-old hotel in downtown Grass Valley. A San Francisco native, Garfinkel launched a real estate career in his hometown prior to moving to the foothills a decade ago. He'd fallen in love with the city's historic buildings and spent years buying, restoring and renting treasured urban relics. When the Holbrooke Hotel came up for sale in 2010, despite ongoing projects in the Bay Area, Garfinkel jumped at the chance and went in with eyes wide open."I knew …