Highlight new rows since the last refresh in All Messages

[ramonsmits]

Stacked on:

• All Messages view no longer disabled during slow queries #3105
• Date/recent time-range picker and a bounded-by-default All Messages view #3106
• Stop the audit capability probe from scanning the whole store #3109
• Augment the query bar with a refresh/cancel option, group the Show and Sort options, and add a "locale/UTC" time selection #3110
• List recent searches under the All Messages search field #3111
• Use a relative timestamp for the All Messages view Time sent column #3112

Under auto-refresh, new messages simply appeared at the top of All Messages with nothing to tell them apart from the rows that were already there. No results view in ServicePulse had an arrival animation to reuse (the saga diagram's border blink is the only one-shot animation and targets diagram nodes), so this adds one.

• The store records which rows are new: the ids of a result that were absent from the previous result of the same query (endpoint, time-range expressions, filter, page size and sort unchanged). The list is empty for the first result, whenever the query itself changed, and for the result after a failure: in those cases every row is different and highlighting all of them says nothing
• Those rows slide in and glow: a short slide-down while fading in, then a light blue tint that fades over three seconds so it stays visible between auto-refresh ticks. Rows are keyed by id, so a new row is a fresh element and the animation plays exactly once on insertion
• Reduced motion keeps the tint and drops the movement

Alternatives considered: a TransitionGroup would also animate rows shifting down, but its enter transition fires for every re-keyed insert, including a completely new query, and cannot be asserted in the component tests. The explicit marker is deterministic and covered by store and list tests.