Move some constants to common (#11004)

### What problem does this PR solve?

As title.

### Type of change

- [x] Refactoring

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

api/db/services/tenant_llm_service.py

@@ -17,7 +17,7 @@ import os
 import logging
 from langfuse import Langfuse
 from api import settings
-from api.db import LLMType
+from common.constants import LLMType
 from api.db.db_models import DB, LLMFactories, TenantLLM
 from api.db.services.common_service import CommonService
 from api.db.services.langfuse_service import TenantLangfuseService