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>

lang/ca/panel.php

@@ -161,6 +161,7 @@ return [
             'redirects' => 'Redireccions',
             'pages' => 'Pàgines',
             'categories' => 'Categories',
+            'webhooks' => 'Webhooks',
             'users' => 'Usuaris',
             'roles' => 'Rols',
             'settings' => 'Configuració',