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/ratelimit.go

@@ -63,7 +63,7 @@ const (
 
 	// receiverAggregateMultiplier scales the configured
 	// per-entrypoint receiver limit into the aggregate limit one
-	// client IP may spend across the whole /webhook/* route. Ten
+	// client IP may spend across the whole /h/* route. Ten
 	// entrypoints' worth lets a single sender address drive several
 	// entrypoints at their full rate, while still capping what one
 	// address costs the unauthenticated receiver.
@@ -390,7 +390,7 @@ func (m *Middleware) postRateLimit(
 // It is Config.ReceiverRateLimit requests per minute.
 //
 // That limit alone bounds nothing in aggregate. The route pattern
-// /webhook/{uuid} matches any single segment, so a client that
+// /h/{uuid} matches any single segment, so a client that
 // invents a fresh path per request mints a fresh bucket per request
 // and never refills one — and every such request still reaches the
 // handler's entrypoint lookup before it 404s. The outer limit is