A Family Legacy In the heart of old Milano, down the winding via Morigi, there is a magical shop from another century, with antique polished wooden counters, trays of jewels lit with a soft glow, and countless drawers, each labeled in an elegant hand , glass, crystal, earrings Tall and thin, Donatella Pellini moves with the grace of a dancer in this hide-away that she calls her headquarters and laboratory.         Like her mother and grandmother before her, Donatella designs exquisite jewelry, but for all the weight of family tradition, her art is uniquely her own.         In 1947, Emma Caimi Pellini first created jewelry for the haute couture houses of Paris, and soon after was recognized by the exclusive fashion houses of her own Milan. Her daughter Carla shared her mother's talent, and went on to open the first store on via Morigi. In 1972, the legacy passed to the gifted hands of Donatella and her brother Ernesto, who heads up business affairs with great savvy.         Much has happened since then. Pellini jewelry is represented all over the world, with show-rooms in many foreign cities. Donatella's designs have been honored at the Triennale in Milan and the Victoria & Albert Museum in London. In 1990 a second store opened in Milan in the via Santa Maria alla Porta, and in 1996 another in via Manzoni. But the creative center remains in via Morigi, in her mother's store.