BEIRUT — Nawaf Salam, the head of the International Court of Justice, won enough support to become Lebanon’s next prime minister after a majority of lawmakers backed him for the post on Monday, a big blow to Hezbollah which accused opponents of working to exclude it. The support for Salam underlined the major shift in the power balance among Lebanon’s sectarian factions since the Shi’ite group Hezbollah was pummeled in a war with Israel last year, and its Syrian ally Bashar al-Assad was toppled. Senior Hezbollah lawmaker Mohammed Raad, whose Iran-backed group had wanted incumbent Najib Mikati to stay in