Event log: show attempt and delivery times, label replays, zone event times (closes #386)

In the event log and on an event's page, attempts and deliveries showed no time, event times had no zone, and a replay looked like the original it repeated. Each attempt now shows when its result was recorded and each delivery when it was created, as how long ago with the full UTC time on hover, and the event log's event times read the same way. A delivery created by Replay records it in a new `replay` column and is labelled a replay in the event's summary line and its delivery list; replays made before this change are not labelled. A delivery's row is now drawn by one template, `delivery_row`, that both pages share.

Model: opus-5-5

templates/delivery_row.html

@@ -0,0 +1,16 @@
+{{define "delivery_row"}}
+<!-- The line that heads a delivery, as handlers.DeliveryView holds it:
+     in the event log, inside the button that shows its attempts, and on
+     an event's own page. Spans only, since a button may hold no div. -->
+<span class="flex flex-1 flex-wrap items-center justify-between gap-3">
+    <span class="flex flex-wrap items-center gap-3">
+        <span class="text-sm text-gray-700">{{.Target.DisplayName}}</span>
+        {{if .Replay}}<span class="text-xs text-gray-500">replay</span>{{end}}
+        <span class="text-xs {{if eq .Status "delivered"}}text-green-600{{else if eq .Status "failed"}}text-red-600{{else if eq .Status "retrying"}}text-yellow-600{{else}}text-gray-400{{end}}">{{with .Paused}}waiting: target paused after repeated failures, next try no earlier than {{.Until}} ({{.Relative}}){{else}}{{.Status}}{{end}}</span>
+    </span>
+    <span class="flex flex-wrap items-center gap-3">
+        <span class="text-xs text-gray-400" title="{{.CreatedUTC}}">created {{.Created}}</span>
+        <span class="text-xs text-gray-400">{{.AttemptCount}} attempt{{if ne .AttemptCount 1}}s{{end}}</span>
+    </span>
+</span>
+{{end}}