A new staging of Beethoven’s “Fidelio’’ opened at San Francisco Opera last week. While the opera was originally set in an 18th century prison, this production places the action in a modern prison setting, a rotating steel cage jammed with inmates and guards. The story revolves around Leonore, a young woman who has taken a job in the prison disguised as a man named Fidelio in order to search for her husband Florestan, a political prisoner close to death from torture and starvation. Beethoven’s only opera is a probing commentary on tyranny in the composer’s time, and director Matthew Ozawa and designer Alexander Nichols make the case for contemporary relevance powerfully, showing women prisoners being brutalized by guards, male inmates kicked and beaten and everyone mercilessly shadowed by flashing video monitors.