Function export_with_page_size 

pub async fn export_with_page_size(
    t: &Transport,
    f: &CaseFilter,
    per_page: u32,
    limit: Option<usize>,
) -> Result<Vec<Case>>

The paging loop with an explicit page size, exposed for tests. Stops paging as soon as limit rows are in hand, mirroring alerts_ops::export’s shape.