Add option to prevent editors from deleting old videos

[vinybk]

Describe the problem to be solved

First of all, massive thanks for implementing channel editors in version 8. As an agency that uploads content for users across self-hosted instances, it is really a game change for us.

We noticed a new concern: a rogue editor can delete old videos in a managed channel. If they delete many videos we would notice and can restore from backups. But if only a few are removed, this might go unnoticed.

Describe the solution you would like

Add a per-channel (or per-editor) option to prevent editors from deleting videos older than X days (7, 30, etc).

This would still allow editors to delete recently uploaded videos (useful when an upload needs to be redone), while protecting older content from accidental or malicious deletion.