feat: Add doc IDs to the session chat response

[whiterabbit1983]

:rocket: This description was created by Ellipsis for commit a4b2f564042fad9de6dcd215ed50455dfbe689fc

Summary:

This PR enhances data traceability in chat interactions by introducing document IDs to the session chat response.

Key points:

• Added DocIds model to openapi_model.py to include document IDs in chat responses.
• Modified proc_mem_context_query in proc_mem_context.py to fetch and pass document IDs.
• Updated session_chat in routers.py to handle document IDs in the chat response.
• Adjusted session handling in session.py to include document IDs in the response setup.
• Enhanced data traceability in chat interactions.

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