Add "Put Back" button to cancel accidental discard draws

When you accidentally click the discard pile, you can now put the card
back instead of being forced to swap. The "Put Back" button appears
only when you've drawn from the discard pile.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

server/game.py

@@ -1051,6 +1051,45 @@ class Game:
             return False
         return True
 
+    def cancel_discard_draw(self, player_id: str) -> bool:
+        """
+        Cancel a draw from the discard pile, putting the card back.
+
+        Only allowed when the card was drawn from the discard pile.
+        This is a convenience feature to undo accidental clicks.
+
+        Args:
+            player_id: ID of the player canceling.
+
+        Returns:
+            True if cancel was successful, False otherwise.
+        """
+        player = self.current_player()
+        if not player or player.id != player_id:
+            return False
+
+        if self.drawn_card is None:
+            return False
+
+        if not self.drawn_from_discard:
+            return False  # Can only cancel discard draws
+
+        # Put the card back on the discard pile
+        cancelled_card = self.drawn_card
+        cancelled_card.face_up = True
+        self.discard_pile.append(cancelled_card)
+        self.drawn_card = None
+        self.drawn_from_discard = False
+
+        # Emit cancel event
+        self._emit(
+            "draw_cancelled",
+            player_id=player_id,
+            card={"rank": cancelled_card.rank.value, "suit": cancelled_card.suit.value},
+        )
+
+        return True
+
     def discard_drawn(self, player_id: str) -> bool:
         """
         Discard the drawn card without swapping.