Warranty callbacks: dispatch, the original work order, and a prevention note to close

Three gaps in warranty callbacks are closed:

• Dispatch. An open callback has a Dispatch button. Pick who's going and the date, and the callback moves to Dispatched. Logging the first visit also counts as dispatch: it records the date (and the person, if they're a team member) and moves the callback to In progress. Before, callbacks went straight from Open to Closed.
• Original work order. Link a callback to the work order it came back on, from the callback itself.
• Prevention note to close. Closing a callback now needs a Prevention Recommendation: what would stop this happening on the next job. If there's genuinely nothing to change, say why. The note feeds Lessons Learned, so a callback closed without one taught the team nothing.