fix(#9552): migrate stale target state for interval turnover

[dianabarsan]

Description

9552

Code review checklist

• [ ] Readable: Concise, well named, follows the style guide, documented if necessary.
• [ ] Documented: Configuration and user documentation on cht-docs
• [ ] Tested: Unit and/or e2e where appropriate
• [ ] Internationalised: All user facing text
• [ ] Backwards compatible: Works with existing data and configuration or includes a migration. Any breaking changes documented in the release notes.

Compose URLs

If Build CI hasn't passed, these may 404:

• Core
• CouchDB Single
• CouchDB Cluster

License

The software is provided under AGPL-3.0. Contributions to this project are accepted under the same license.

[dianabarsan]

I was really tempted to do this last time I "fixed" this, but thought it was too hard-handed. And now I'm only doing it on load, because I think migrating it pre-calculation is also too hard-handed. Leaving this for the reviewer to decide.