fixes #4; lock champions at beginning of turn

src/model/turn.py

@@ -158,7 +158,9 @@ class Turn(Serializable):
         return True
 
     async def start_turn(self) -> None:
-        pass
+        for c in self.player.board:
+            if c.card_type == CardType.CHAMPION:
+                self.lock_card(str(c.card_id))
 
     def serialize(self):
         data = super().serialize() | {