feat: enhance new chat functionality with document mentions support

- Updated the new chat routes to include handling for mentioned document IDs, allowing users to reference specific documents in their chat.
- Modified the NewChatRequest schema to accommodate optional document IDs.
- Implemented document mention formatting in the chat streaming service for improved context.
- Enhanced the frontend to manage document mentions, including a new atom for state management and UI updates for document selection.
- Refactored the DocumentsDataTable component for better integration with the new mention functionality.

surfsense_backend/app/routes/new_chat_routes.py

@@ -686,7 +686,7 @@ async def handle_new_chat(
         search_space = search_space_result.scalars().first()
 
         # TODO: Add new llm config arch then complete this
-        llm_config_id = -1  
+        llm_config_id = -4
 
         # Return streaming response
         return StreamingResponse(
@@ -698,6 +698,7 @@ async def handle_new_chat(
                 llm_config_id=llm_config_id,
                 messages=request.messages,
                 attachments=request.attachments,
+                mentioned_document_ids=request.mentioned_document_ids,
             ),
             media_type="text/event-stream",
             headers={