[Request] Add ability to send PDF/files without embedings

[stone-w4tch3r]

🥰 Feature Description

Modern models such as claude/gpt4o/o1 have perfect native support for PDF and some other file formats. But Lobe currently works with such files only via RAG/embeddings, which is not optimal for those models

🧐 Proposed Solution

Add ability to send files directly to models, without any embeddings processing.

📝 Additional Information

This is claude's PDF API guide, just as example: https://docs.anthropic.com/en/docs/build-with-claude/pdf-support