Make every clickable control look clickable, in two shared styles (closes #375)

Buttons keep btn-primary, btn-secondary and btn-danger and gain a
pointer cursor; the site name and the navigation links become
btn-secondary buttons. Every control that was plain coloured text
(Copy, both Add, the row actions, Resubmit, Replay, the back, footer
and download links) now uses btn-small, bordered at rest with hover
and focus states. Each card on the webhook list shows an Open label in
btn-small and takes its focus outline. Both styles are in
static/css/style.css, which the layout now loads.

The event log's clickable rows become buttons, so they work by
keyboard; Replay moves beside its delivery's row. Rows on the webhook
page and in the event log wrap at phone width. The browser test now
checks that Copy reads "Copied".

Model: opus-5-5

templates/htmlheader.html

@@ -3,6 +3,7 @@
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>{{block "title" .}}Webhooker{{end}}</title>
 <link rel="stylesheet" href="/s/css/tailwind.css">
+<link rel="stylesheet" href="/s/css/style.css">
 <style>[x-cloak] { display: none !important; }</style>
 {{block "head" .}}{{end}}
 {{end}}