Prevent user to open multiple strategy on the same ticker

src/Managing.Application/ManageBot/StartBotCommandHandler.cs

@@ -43,6 +43,15 @@ namespace Managing.Application.ManageBot
                     $"Bot trading balance must be greater than {Constants.GMX.Config.MinimumPositionAmount}");
             }
 
+            // Check if user already has a bot on this ticker
+            var hasExistingBotOnTicker = await _botService.HasUserBotOnTickerAsync(request.User.Id, request.Config.Ticker);
+            if (hasExistingBotOnTicker)
+            {
+                throw new InvalidOperationException(
+                    $"You already have a strategy running or saved on ticker {request.Config.Ticker}. " +
+                    "You cannot create multiple strategies on the same ticker.");
+            }
+
             Account account;
             if (string.IsNullOrEmpty(request.Config.AccountName))
             {