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>

rag/app/audio.py

@@ -18,7 +18,7 @@ import os
 import re
 import tempfile
 
-from api.db import LLMType
+from common.constants import LLMType
 from api.db.services.llm_service import LLMBundle
 from rag.nlp import rag_tokenizer, tokenize