chore: Update database configuration and enhance error handling

- Changed database credentials in start.sh for testing purposes.
- Added environment variable for testing and allowed origins in start.sh.
- Improved error handling in yggdrasil_auth_service.go by checking for nil user before returning an error.

internal/service/yggdrasil_auth_service.go

@@ -42,6 +42,9 @@ func (s *yggdrasilAuthService) GetUserIDByEmail(ctx context.Context, email strin
 	if err != nil {
 		return 0, apperrors.ErrUserNotFound
 	}
+	if user == nil {
+		return 0, apperrors.ErrUserNotFound
+	}
 	return user.ID, nil
 }