feat(admin): star/tags marks, service product-type filter, campaign bulk actions, SMTP test

- Star (is_starred) and colored tags for services, customers, orders, invoices:
  Markable trait, tags/taggables tables, PATCH administrator/marks/{type}/{key},
  tag CRUD, list filters starred / tag_ids[]
- GET administrator/services accepts product_type (falls back to product type
  for legacy rows without services.type)
- Mail campaigns: bulk cancel / retry failed / delete; cancelled campaigns are
  skipped by SendMailCampaignRecipient
- POST administrator/settings/test-smtp sends a test email through the saved
  mail transport

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

app/Support/MailSettings.php

@@ -44,6 +44,11 @@ final class MailSettings
         Config::set('mail', $config);
     }
 
+    public static function transport(): ?string
+    {
+        return self::resolve()['transport'] ?? null;
+    }
+
     public static function refresh(object $mailer): void
     {
         self::apply();