Added CancellationTokenSource per-load in both DetailsIslandViewModel
and TasksIslandViewModel. Public entry points cancel any in-flight load
before starting a new one. DB calls and collection mutations after awaits
are guarded with ThrowIfCancellationRequested. DetailsIslandViewModel
now sets _subscribedTaskId only after the DB confirms the entity exists,
preventing the SignalR handler from routing messages to a stale load.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
62aac7eedb