Job scheduler

:::info Status Outline — expand with a full worked example (e.g. registering a new scheduled job). :::

The job scheduler is built on Quartz.NET, with a Kandra-specific ICallerContext seam so a scheduled job runs as a specific user (and in that user's time zone), rather than in an ambient/system identity — important for anything a job does that goes through the normal ISubmitScope/audit-trail path.