Automated monitoring of media

Problem/Motivation

The module’s queue must currently be populated manually through the admin form or Drush. Cron processes items that are already queued, but it does not scan the media library or enqueue items on a schedule. As a result, an oEmbed resource that becomes unavailable after its media item was saved can remain undetected until someone manually starts a validation run.

A configurable automated queueing feature would periodically find oEmbed media items and enqueue them for validation, while preserving the existing manual queue controls.

Steps to reproduce

1. Enable the module and configure an oEmbed media type.
2. Create a media item with an oEmbed URL that later becomes unavailable, without manually queueing a validation run.
3. Ensure the validation queue is empty, then wait past the configured run interval and run cron.
4. Check the queue and invalid-items report. The item has not been queued or revalidated; it is detected only after manually starting a queue run.