Keep orphans option when deleting CronWorkflows in UI

# Summary

When deleting a CronSchedule in the Workflows UI, any Workflows spawned from that CronSchedule will also be deleted (garbage collected by Kubernetes). This behaviour isn't obvious when a user goes to delete a Cron workflow and may lead to them losing data.

I propose that an option should be added to the delete confirmation modal that allows users to keep any orphaned Workflows from the CronSchedule. Alternatively, improved messaging in the modal that states any Workflows will be lost.

## Use Cases

When a user wishes to delete a CronSchedule but keep any of its associated Workflows

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The issue does not name files or tests; start by locating the CronSchedule delete confirmation modal and checking how Kubernetes garbage collection handles spawned Workflows. Done means the modal either offers a keep-orphans option or clearly warns that associated Workflows will be deleted, with the chosen behavior verified in the UI.

Written by the indexing model from the issue text.