How can I put a mirror on the inside of a wardrobe if the shelves come all the way to the door?
You'll have to remove the shelves and have the and have the edges cut to make room for the mirror.
There's a possibility that the actual hinges and opener could be adjusted to allow for the additional space. The mirror could be assembled using mirror tiles from your home store and heavy duty double sided tape.
As a last resort, you could mount a mirror on the wall inside the cabinet... of course you'd loose some hang up space. The mirror could also be mounted on the outside of the door which might work better since the doors only open 90 degrees.