Fix keycard mismatch and typo in locked-door message

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".

doom_matrix/entities/items.py

@@ -78,7 +78,8 @@ class Inventory:
 
     def add(self, item, count=1):
         if item.kind == "key":
-            self.keycards.add(item.item_id)
+            color = item.item_id.removeprefix("keycard_")
+            self.keycards.add(color)
             return
         if item.kind == "fragment":
             self.crucible_fragments += count