Show 50 recent events with size, processing time and status (closes #347)

The recent events list on a webhook's page, now headed "50 Most Recent
Events", shows the 50 newest events, each with its time relative to now
(the full UTC timestamp on hover), its body size, its processing time
and, when the webhook has exactly one HTTP target, that target's last
HTTP status, colour-coded. Resubmitted copies are marked, as in the
event log.

Each event now records its body's size in bytes when it is stored, on
receipt and on resubmit, and the list reads that instead of the body.
Processing time is read from the existing delivery and attempt
timestamps. The list loads its deliveries and their attempts in batched
queries of its own, reading only the columns it shows. A failed load
answers with an error instead of an empty list.

Model: opus-5-5

templates/source_detail.html

@@ -181,18 +181,30 @@
     <!-- Recent Events -->
     <div class="card mt-6">
         <div class="p-4 border-b border-gray-200 flex justify-between items-center">
-            <h2 class="text-lg font-medium text-gray-900">Recent Events</h2>
+            <h2 class="text-lg font-medium text-gray-900">50 Most Recent Events</h2>
             <a href="/source/{{.Webhook.ID}}/logs" class="btn-text text-sm">View All</a>
         </div>
         <div class="divide-y divide-gray-100">
             {{range .Events}}
             <div class="p-4">
-                <div class="flex items-center justify-between">
-                    <div class="flex items-center gap-3">
+                <div class="flex flex-wrap items-center justify-between gap-3">
+                    <div class="flex flex-wrap items-center gap-3">
                         <span class="badge-info">{{.Method}}</span>
-                        <span class="text-sm text-gray-500">{{.ContentType}}</span>
+                        <span class="text-sm text-gray-500 break-all">{{.ContentType}}</span>
+                        {{if .ResubmittedFromID}}
+                        <span class="text-xs text-gray-500" title="This event is a copy of {{.ResubmittedFromID}}">resubmitted copy</span>
+                        {{end}}
+                    </div>
+                    <div class="flex flex-wrap items-center gap-3 text-xs text-gray-400">
+                        <span title="Body size">{{.Size}}</span>
+                        {{if .ProcessingTime}}
+                        <span title="Processing time: how long the slowest delivery took, from being queued to its last attempt">{{.ProcessingTime}}</span>
+                        {{end}}
+                        {{if .Status}}
+                        <span class="font-medium {{.StatusClass}}" title="HTTP status from the HTTP target">{{.Status}}</span>
+                        {{end}}
+                        <span title="{{.ReceivedUTC}}">{{.Received}}</span>
                     </div>
-                    <span class="text-xs text-gray-400">{{.CreatedAt.Format "2006-01-02 15:04:05 UTC"}}</span>
                 </div>
             </div>
             {{else}}