Returns a list of report instances that the user can access.

    Report instances represent specific generations of reports with data from selected documents.
    Each instance has a status indicating its processing state.
    
    Query Parameters:
    - status: Filter by status (ready, processing, completed, failed)
    - report__hashid: Filter by report ID (only returns instances of that specific report)
    - folder_id: Filter by folder ID (only returns instances linked to file records in that folder)
    - search: Search report instances by user prompt, LLM prompt, or report name (case-insensitive partial match)
    - include_deleted: Include soft-deleted report instances in results (default: false)