Enhance Event admin UI and fix translations

- Remove default_locale and primary_join_token columns from event list
- Add read-only join link field to event edit form
- Add missing translations for used/remaining photos and join link
- Fix array-to-string conversion error in join link modal

resources/lang/de/admin.php

@@ -365,13 +365,15 @@ return [
             'default_locale' => 'Standardsprache',
             'is_active' => 'Aktiv',
             'settings' => 'Einstellungen',
+            'join_link' => 'Einladungslink',
         ],
         'table' => [
             'tenant' => 'Mandant',
             'join' => 'Beitreten',
             'join_tokens_total' => 'Einladungen: :count',
-            'join_tokens_missing' => 'Noch keine Einladungen erstellt',
             'package' => 'Paket',
+            'used_photos' => 'Fotos',
+            'remaining_photos' => 'Verbleibend',
         ],
         'relation_managers' => [
             'event_packages' => [