fix(settings): Disable app again if it breaks the files app

[susnux]

Summary

Apps can no longer hard break the server core, see also #44014 , but they still might break the files app.
This is and was tested, but it only set on the UI.

So if it fails it now also:

1. Show an visible error toast
2. Disable the app again

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[susnux]

/backport to stable28