feat(sync): добавил cooperative-отмену sync и pipeline-задач

ensureActive в StorageSyncEngine, flush журнала перед чтением, Cancelled
в StorageSyncRunOutcome и TaskContext.ensureNotCancelled.

app/src/main/java/com/github/nullptroma/wallenc/app/sync/StorageSyncWorker.kt

@@ -29,6 +29,10 @@ class StorageSyncWorker @AssistedInject constructor(
                 Timber.d("Periodic storage sync finished")
                 Result.success()
             }
+            StorageSyncRunOutcome.Cancelled -> {
+                Timber.d("Periodic storage sync cancelled")
+                Result.success()
+            }
             is StorageSyncRunOutcome.Failed -> {
                 Timber.w(outcome.error, "Periodic storage sync failed")
                 Result.retry()