Fix #7184

• Add optional batch delete support to the Delete transform, aligned with the existing Update transform (use_batch + commit size).
• Wire batch execution through Database.insertRow(..., useBatchUpdate, true) and flush remaining batches on dispose via emptyAndCommit().
• Add Use batch deletes checkbox in DeleteDialog, with the same error-handling constraint as Update on databases that do not support batch + error handling together.
• Expand unit tests for all delete plugin classes (meta, SQL generation, batch vs non-batch execution, injection, data model).