The Iranian authorities hanged a 23-year-old man early Tuesday, the latest in a string of executions linked to the large-scale protests that shook the country in the fall of 2022. The man, Mohammad Ghobadlou, who worked in a barbershop, was accused of killing a police officer by running over him with his car. His execution, several months after the last hanging of a protester, illustrated how the government is continuing to crack down on dissent in the wake of that monthslong uprising against the Islamic Republic. “They are killing us one by one,” the actor Ashkan Khatibi wrote on social media in a post that included a picture of Mr. Ghobadlou’s father, a disabled veteran of the Iran-Iraq war, wrapped in a blanket in front of the prison, north of Tehran, where his son was held. The protests were set off by the death of Mahsa Amini, 22, in September 2022 while she was in the custody of the morality police, accused of violating Iran’s hijab law. The months of demonstrations that followed in cities …