Get Evidence By References

Fetch evidence items by their references (tool_call_id + evidence_id).

This endpoint is optimized for batch fetching:

• Groups references by tool_call_id
• Fetches each S3 bundle once
• Filters to requested evidence UUIDs

Args: request: Contains session_id and list of evidence references authorized_user: Authorized user dependency

Returns: JSONResponse with evidence dict mapping evidence_id to enriched evidence