FAS - add audit records for all interactions

FAS - all interactions

1. We need a history of status changes, including who did it, what changed, and who did the change
3. We need history of all refund requests/rejects/approvals
5. We need to track all comments done by staff (don't need history on a comment)
7. All routing slip corrections need to be tracked, and not just as comments
9. Linking should be treated as a status change on both the parent and the child RS. So we need to know who did what when.

Start by mapping the FAS flows for status changes, refunds, staff comments, routing slip corrections, and linking, then identify the backend handlers and persistence models for each interaction. Define done as an audit record capturing the actor, action, changed data, and time for every listed interaction, including both sides of a link.

Written by the indexing model from the issue text.