Handle db validation errors gracefully

[charisk]

We have a mixture of validation checks and unhandled exceptions in various places. This PR aims to tidy that up so that:

• Validation errors are handled gracefully in the UI (DbPanel), using error notifications rather than triggering the global error handler.
• The DbConfigStore throws exceptions in the unlikely event that a caller has asked it to do something that would get the config in an invalid state (e.g. to add a list with an empt name).
• The DbManager should just pass through without doing the same checks.

Checklist

N/A:

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[shati-patel]

Thanks 🧹 A couple of initial comments, just from poking around locally!

[norascheuch]

Looks good, thanks for cleaning this up!

[norascheuch]

Looks good, thanks for cleaning this up!

[shati-patel]

Looks good now, thanks for the fixes 😸