all view controllers with `Task` should have `@MainActor`

[ivan-ushakov]

For some reason @MainActor does not work as expected in case of ADK inheritance. Needs more investigation but for now let's mark @MainActor all our view controllers with at least one Task

[tomholub]

This issue wants to mark the class itself @MainActor while #997 would be marking individual methods @MainActor. Marking individual methods seems better. But was that the issue you had with ADK?

If unsure, we could try that approach first, meaning I'd close this issue in favor of that one.