- TicketModel: add deleteTicket() that removes all child records
(comments, watchers, dependencies, attachments, custom fields)
then deletes the ticket and cleans up physical attachment files
- BulkOperationsModel: add bulk_delete case to processBulkOperation()
so the "Bulk Delete" UI button actually works instead of silently
failing with N failures
- bulk_operation.php: validate operation_type against whitelist to
reject unknown operations early with a proper error
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>