On the French Riviera and Italian coast, in the yacht clubs and shimmering ballrooms, everyone, including Pamela Anderson, wanted to get close to the prince. So did investigators. — Juan Tamenne was neither spy nor detective, but he was on a mission in the spring of 2015 as he watched a scene unfold at Monaco’s Yacht Club, a four-story playground for the impossibly wealthy on the sparkling blue Mediterranean. Tamenne, 46, with straight blonde hair, narrow elegant eyes and…