SAN FRANCISCO — The FBI’s victory in breaking into a San Bernardino killer’s iPhone without Apple’s help merely prolongs a battle over how far the government can go to examine private messages, photos and other files. “There’s a clash of values and interests that I think will continue,” said Ed Black, head of Computer and Communications Industry Association, a trade group whose members include Google, Facebook and Microsoft. Federal prosecutors have appealed a court ruling that said Apple doesn’t have to help them extract data from another iPhone in a New York drug case.