As daily life becomes a struggle, Iranian authorities are tightening their grip, blacking out the internet and erecting more checkpoints.DUBAI — A week of Israeli strikes has upended the lives of Iranians, battering vital infrastructure like fuel depots, airports and public buildings, and shaking the population’s confidence that it could remain insulated from conflicts in the wider Middle East. Now, with President Donald Trump warning that U.S. forces could enter the fray if Iran doesn’t make significant concessions in nuclear negotiations, Iranians fear that another deadlier, even more destructive phase of the conflict could loom. “People are terrified. They don’t...