VULCANO, Sicily — On the Vulcanello promontory, looking onto one of the most cinematic stretches of the Mediterranean, Pierpaolo Tiretti runs Therasia Resort, Sea and Spa, the design-led retreat that occupies a piece of Italian television history. The villa was once Mike Bongiorno’s, the man who effectively invented Italian TV. His celebrity rolodex laid the groundwork for what is today one of the Aeolian Islands’ most discreet hotels.