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.
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

templates/sources_list.html

@@ -6,7 +6,7 @@
 <div class="max-w-6xl mx-auto px-6 py-8">
     <div class="flex justify-between items-center mb-6">
         <h1 class="text-2xl font-medium text-gray-900">Webhooks</h1>
-        <a href="/sources/new" class="btn-primary">
+        <a href="/hooks/new" class="btn-primary">
             <svg class="w-5 h-5 mr-1" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                 <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 4v16m8-8H4"/>
             </svg>
@@ -17,7 +17,7 @@
     {{if .Webhooks}}
     <div class="grid gap-4">
         {{range .Webhooks}}
-        <a href="/source/{{.ID}}" class="card-elevated p-6 block">
+        <a href="/hook/{{.ID}}" class="card-elevated p-6 block">
             <div class="flex justify-between items-start">
                 <div>
                     <h2 class="text-lg font-medium text-gray-900">{{.Name}}</h2>
@@ -42,7 +42,7 @@
         </svg>
         <h2 class="text-lg font-medium text-gray-900 mb-2">No webhooks yet</h2>
         <p class="text-gray-500 mb-6">Create your first webhook to start receiving and forwarding events.</p>
-        <a href="/sources/new" class="btn-primary">Create Webhook</a>
+        <a href="/hooks/new" class="btn-primary">Create Webhook</a>
     </div>
     {{end}}
 </div>