Spoiler alert: If you plan to see Alex Garland’s new movie “Civil War,” then don’t read this until you have. When war photographer Lee Smith closes her eyes during what should be a relaxing bath moment at the end of a busy working day, she sees visions. American soldiers in Iraq and Afghanistan, shell-shocked and staring at her lens. A man shooting another man in the head at close range. Another man, a car tire around his torso, clamping his arms down tight.