Fix tenant event form package selector so it no longer renders empty-value options, handles loading/empty

states, and pulls data from the authenticated /api/v1/tenant/packages endpoint.
    (resources/js/admin/pages/EventFormPage.tsx, resources/js/admin/api.ts)
  - Harden tenant-admin auth flow: prevent PKCE state loss, scope out StrictMode double-processing, add SPA
    routes for /event-admin/login and /event-admin/logout, and tighten token/session clearing semantics (resources/js/admin/auth/{context,tokens}.tsx, resources/js/admin/pages/{AuthCallbackPage,LogoutPage}.tsx,
    resources/js/admin/router.tsx, routes/web.php)

app/Services/Checkout/CheckoutAssignmentService.php

@@ -84,10 +84,16 @@ class CheckoutAssignmentService
             }
 
             if ($user) {
-                Mail::to($user)->queue(new Welcome($user));
+                $mailLocale = $user->preferred_locale ?? app()->getLocale();
+
+                Mail::to($user)
+                    ->locale($mailLocale)
+                    ->queue(new Welcome($user));
 
                 if ($purchase->wasRecentlyCreated) {
-                    Mail::to($user)->queue(new PurchaseConfirmation($purchase));
+                    Mail::to($user)
+                        ->locale($mailLocale)
+                        ->queue(new PurchaseConfirmation($purchase));
                 }
 
                 AbandonedCheckout::query()