Fixs for translation agent (#3557)

### What problem does this PR solve?

#3556 

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)

api/apps/user_app.py

@@ -518,6 +518,7 @@ def user_register(user_id, user):
                 "model_type": llm.model_type,
                 "api_key": settings.API_KEY,
                 "api_base": settings.LLM_BASE_URL,
+                "max_tokens": llm.max_tokens
             }
         )