By Joseph Campbell and Alessandra Prentice ZAPORIZHZHIA, Ukraine (Reuters) -Russia unleashed rockets on Tuesday on an encircled steel works in Mariupol, Ukraine’s last redoubt in the port city, after a ceasefire broke down with some civilians still trapped beneath the sprawling site despite a U.N.-brokered evacuation. However, scores of evacuees who managed to leave under U.N. and Red Cross auspices at the weekend after cowering for weeks under the Azovstal plant finally reached the relative safety of Ukraine-controlled Zaporizhzhia. “We would have hoped that many more people would have been a…