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

static/js/app.js

@@ -70,10 +70,15 @@ document.addEventListener("alpine:init", function () {
     "use strict";
 
     // Something a click shows and hides: the mobile menu, an add form,
-    // an event in the event log, a delivery's attempts.
+    // an event in the event log or in the recent events, a delivery's
+    // attempts. It starts hidden, or shown when its element has the
+    // data-open attribute.
     window.Alpine.data("collapsible", function () {
         return {
             open: false,
+            init() {
+                this.open = this.$root.hasAttribute("data-open");
+            },
             toggle() {
                 this.open = !this.open;
             },