Rather than hanging curtains, you can achieve a really good light seal with foam strip weather stripping, about 3-5mm thick, 1cm wide, comes in coils and is cheap. It has pull off covering for the sticky stuff, which you use to attach. I used it for my darkroom door, top and sides., place it in the contact areas between the door and the jam. It lasts an amazing length of time (in terms of the foam bouncing back). Then just roll up a towel for the crack at the bottom of the door.
The only thing in your situation, is that the adhesive is quite aggressive, and might be hard to remove. So, you need to figure out a way to attach it with enough stick to hold it, and be able to remove it later. Might be able to tape it in place with masking tape, without removing its adhesive cover. Or you could stick it down to plain strips of paper, then attach the paper at intervals to the door jam, then easily removable.