The biggest tech companies are warring over who’s responsible for children’s safety online, with billions of dollars in fines on the line as states rapidly pass conflicting laws requiring companies to verify users’ ages.The struggle has pitted Meta Platforms Inc. and other app developers against Apple Inc. and Alphabet Inc.’s Google, the world’s largest app stores. Lobbyists for both sides are moving from state to state, working to water down or redirect the legislation to minimize their clients...