Add recipient email and milestone notifications on transfer create.

Recipients can be emailed the download link immediately and at optional
reminders (7/3/1 days before unavailable, or when grace period starts).

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Services/Transfer/TransferBillingService.php

@@ -102,6 +102,8 @@ class TransferBillingService
             'grace_ends_at' => $graceEndsAt,
             'expires_at' => $graceEndsAt,
         ]);
+
+        app(TransferRecipientMailService::class)->notifyRecipient($transfer->fresh(), 'grace');
     }
 
     public function processDueRenewals(): array