feat: add Weeztix OAuth, coupon codes, and Mailwizz mapping

Implement Weeztix integration per documentation: database config and
subscriber coupon_code, OAuth redirect/callback, admin setup UI with
company/coupon selection via AJAX, synchronous coupon creation on public
subscribe with duplicate and rate-limit handling, Mailwizz field mapping
for coupon codes, subscriber table and CSV export, and connection hint
on the pages list.

Made-with: Cursor

app/Jobs/SyncSubscriberToMailwizz.php

@@ -134,6 +134,11 @@ class SyncSubscriberToMailwizz implements ShouldBeUnique, ShouldQueue
             }
         }
 
+        $couponField = $config->field_coupon_code;
+        if (is_string($couponField) && $couponField !== '' && $subscriber->coupon_code !== null && $subscriber->coupon_code !== '') {
+            $data[$couponField] = $subscriber->coupon_code;
+        }
+
         return $data;
     }