Move some constants to common (#11004)

### What problem does this PR solve?

As title.

### Type of change

- [x] Refactoring

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

rag/app/naive.py

@@ -28,7 +28,7 @@ from markdown import markdown
 from PIL import Image
 from tika import parser
 
-from api.db import LLMType
+from common.constants import LLMType
 from api.db.services.llm_service import LLMBundle
 from rag.utils.file_utils import extract_embed_file, extract_links_from_pdf, extract_links_from_docx, extract_html
 from deepdoc.parser import DocxParser, ExcelParser, HtmlParser, JsonParser, MarkdownElementExtractor, MarkdownParser, PdfParser, TxtParser