Shortens character names throughout dialogue, save.py loop-twist lines,
and README. Adds three wallpaper images to Wallpaper/ and embeds
Doom_Slyer.png as the README screenshot.
Inventory stored keycards under their full item_id (keycard_red) while
Room.locked_by/has_keycard checked against the plain color (red), so
the Waffentresor always reported itself as locked even with the
keycard in hand. Also fixes "rede Keycard" -> "rote Keycard".