Send signed outgoing webhooks

Fed by the records themselves, delivered only to public HTTPS addresses
checked at every attempt, retried, and switched off after repeated failures.
A submitter's details travel only to webhooks that opted into them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/Support/Permissions.php

@@ -73,6 +73,10 @@ final class Permissions
         // the provider's rate limit, which is a shared resource.
         'repositories' => ['view_any', 'view', 'create', 'update', 'delete', 'sync'],
 
+        // Where the site tells other systems what happened. A webhook sends
+        // data off this server, so it is an administrator's decision.
+        'webhooks' => ['view_any', 'view', 'create', 'update', 'delete'],
+
         'users' => ['view_any', 'view', 'create', 'update', 'delete'],
         'roles' => ['view_any', 'view', 'create', 'update', 'delete'],