CVE-2026-54529: SQLAdmin: Unvalidated sortBy parameter in `ModelView` bypasses `column_sortable_list`

ModelView.sort_query() uses the attacker-controlled sortBy list-view query parameter without checking it against the configured column_sortable_list allow-list. The value is resolved with getattr(model, ...) and fed into relationship joins and order_by(), so a request can sort by any column of the model — including ones hidden from column_list — and, via a dotted path, by columns of related models. Because row order then reflects the value of an unexposed column, this is an information-exposure ordering oracle.