post https://api.flextract.dev/api/reports//create_instance/
Create a report instance with data injection from file records.
Body Parameters:
- user_prompt: Optional user-provided prompt or instructions
- file_records: List of file record IDs to include in the report
- folder_id: Folder ID to filter file records (alternative to file_records)
Returns a JSON response with the task ID, report instance ID, and report ID for tracking.