Show each webhook's activity in the webhook list (closes #394)

Each entry in the webhook list now shows when the webhook's last event
arrived, or "No events yet", and how many of its deliveries failed in
the last 24 hours, in red when that is not zero. The entrypoint and
target counts say how many are inactive.

The figures come from the statistics pane's own reads: the event totals
row, which now also gives the event count, shown as events within
retention, instead of counting every stored event, and the pane's query
over the deliveries finished in the last 24 hours. A webhook whose event
database cannot be read says so in its entry rather than showing zeros.

Model: opus-5-5

templates/sources_list.html

@@ -27,10 +27,16 @@
                 </div>
                 <span class="badge-info">Retention: {{.RetentionLabel}}</span>
             </div>
-            <div class="flex gap-6 mt-4 text-sm text-gray-500">
-                <span>{{.EntrypointCount}} entrypoint{{if ne .EntrypointCount 1}}s{{end}}</span>
-                <span>{{.TargetCount}} target{{if ne .TargetCount 1}}s{{end}}</span>
-                <span>{{.EventCount}} event{{if ne .EventCount 1}}s{{end}}</span>
+            <div class="flex flex-wrap gap-6 mt-4 text-sm text-gray-500">
+                <span>{{.EntrypointCount}} entrypoint{{if ne .EntrypointCount 1}}s{{end}}{{if .InactiveEntrypointCount}}, {{.InactiveEntrypointCount}} inactive{{end}}</span>
+                <span>{{.TargetCount}} target{{if ne .TargetCount 1}}s{{end}}{{if .InactiveTargetCount}}, {{.InactiveTargetCount}} inactive{{end}}</span>
+                {{if .EventsUnreadable}}
+                <span class="text-red-600">The event figures could not be read.</span>
+                {{else}}
+                <span>{{.EventCount}} event{{if ne .EventCount 1}}s{{end}} within retention</span>
+                <span>{{with .LastEventAt}}Last event {{.UTC.Format "2006-01-02 15:04:05 UTC"}}{{else}}No events yet{{end}}</span>
+                <span class="{{if .FailedLast24Hours}}font-medium text-red-600{{end}}">{{.FailedLast24Hours}} failed deliver{{if eq .FailedLast24Hours 1}}y{{else}}ies{{end}} in the last 24 hours</span>
+                {{end}}
             </div>
         </a>
         {{end}}