Jumoo.Processing: pipeline cancellation, cache pruning, 18.1.1 release

Jumoo.Processing: ported cancellation token support forward from v17/main to v18/main — IPipelineService.Process and IProcessingService.ProcessAsync now accept a CancellationToken so an aborted source request can stop mid-step instead of running to completion (old overloads obsoleted, removed in v20)
Jumoo.Processing: added a recurring job that prunes Completed/Failed rows from the pipeline cache table older than KeepFinishedPipelinesForHours (default 72h) — the table only ever grew before this
Released 18.1.1 to NuGet