Move webhook pages to /hook/ID and inbound URLs to /h/UUID (closes #367)

The webhook page and everything under it move from /source/ID to
/hook/ID, the list and new-webhook form to /hooks and /hooks/new, and
the event log from .../logs to /hook/ID/events, body download
included. Entrypoint URLs move from /webhook/UUID to /h/UUID, and the
webhook page shows only that form. The old paths are gone.

Links, redirects, form actions, tests, comments and the README follow.
Both links to the event log page, and its title and heading, now read
"Full Event Log". Go identifiers and template file names are
unchanged. A new route test posts to the entrypoint URL the webhook
page shows and checks that the receiver rate limit applies to it.

Model: opus-5-5

internal/middleware/middleware.go

@@ -257,7 +257,7 @@ func concreteLogURL(r *http.Request) string {
 //
 // 3xx and 4xx responses get the chi route pattern instead. Those are
 // the outcomes an unauthenticated client drives for free: 404 or 429
-// on any invented /webhook/ path, 303 to the login page on any
+// on any invented /h/ path, 303 to the login page on any
 // invented /user/ path. Logging the concrete URL there lets a flood
 // write attacker-chosen text, of attacker-chosen length, into the
 // operator's log at one line per request. The pattern comes from the
@@ -560,7 +560,7 @@ func (s *Middleware) MaxBodySize(
 				// internal/server/routes.go), so an
 				// unauthenticated client reaches it with a path
 				// of its own choosing and its own length —
-				// POST /source/<8 KB>/edit with an oversize
+				// POST /hook/<8 KB>/edit with an oversize
 				// declared Content-Length costs nothing to
 				// send. At WARN, on by default, that is a
 				// write into the operator's log sized by the