Implement critical security fixes from code review

LittleShop/Controllers/AuthController.cs

@@ -38,7 +38,7 @@ public class AuthController : ControllerBase
         catch (Exception ex)
         {
             _logger.LogError(ex, "Error during login for user: {Username}", loginDto.Username);
-            return StatusCode(500, new { message = "An error occurred during login", error = ex.Message });
+            return StatusCode(500, new { message = "An error occurred during login" });
         }
     }
 }