Give each event its own page and show bodies the same everywhere (closes #369)

Each row of the recent events on the webhook page links to the
event's own page, /hook/{id}/events/{eventID}, and expands to show its
body; only the newest starts expanded. The event's page shows its
details, its whole body and every delivery with its attempts.

One renderer, newBodyView with templates/event_body.html, shows a body
in all three places: whole up to 32 KiB, cut there in the lists with a
link to the event's page, JSON pretty-printed, a body of more than 200
lines or 32 KiB in a scrolling box, and a body that is not text left
out beside its download link. A resubmitted copy links to its
original's page.

Model: opus-5-5

internal/handlers/export_test.go

@@ -19,10 +19,16 @@ func (s *Handlers) SetLogForTest(log *slog.Logger) {
 	s.log = log
 }
 
-// MaxRenderedBodyBytesForTest exposes the event log's body cap
-// to the handlers_test package.
+// MaxRenderedBodyBytesForTest exposes the body cap of the lists
+// of events to the handlers_test package.
 const MaxRenderedBodyBytesForTest = maxRenderedBodyBytes
 
+// NewBodyViewForTest exposes newBodyView for use in the
+// handlers_test package.
+func NewBodyViewForTest(body []byte, size int64) BodyView {
+	return newBodyView("/hook/w/events/e", body, size)
+}
+
 // MaxRenderedResponseBytesForTest exposes the event log's
 // delivery response cap to the handlers_test package.
 const MaxRenderedResponseBytesForTest = maxRenderedResponseBytes