fix(api): hide sensitive fields by default

Add model-level hidden fields for secrets, tokens, keys, notification
credentials, deployment logs, and environment values. Allow explicit
read:sensitive API access to reveal gated private keys and deployment logs,
and cover the behavior with feature and unit tests.

app/Models/WebhookNotificationSettings.php

@@ -33,6 +33,10 @@ class WebhookNotificationSettings extends Model
         'traefik_outdated_webhook_notifications',
     ];
 
+    protected $hidden = [
+        'webhook_url',
+    ];
+
     protected function casts(): array
     {
         return [