feat: add short_code field to device login API

- Add optional short_code parameter to DeviceLoginRequest
- Add ShortCode field to Device model
- Save short_code to database during device registration
- Add database migration for user_device.short_code column
- Fix duplicate variable declaration in routes.go

internal/logic/auth/deviceLoginLogic.go

@@ -197,6 +197,7 @@ func (l *DeviceLoginLogic) registerUserAndDevice(req *types.DeviceLoginRequest)
 			UserId:     userInfo.Id,
 			UserAgent:  req.UserAgent,
 			Identifier: req.Identifier,
+			ShortCode:  req.ShortCode,
 			Enabled:    true,
 			Online:     false,
 		}