Cancel animations on game leave to prevent overlay flash on lobby

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/app.js

@@ -3057,6 +3057,9 @@ class GolfGame {
     }
 
     showLobby() {
+        if (window.cardAnimations) {
+            window.cardAnimations.cancelAll();
+        }
         this.showScreen(this.lobbyScreen);
         this.lobbyError.textContent = '';
         this.roomCode = null;