Fix transfer share links and redesign recipient download email.

Use transfer.ladill.com share URLs in notifications and APIs, add the email
logo, and show file details with a prominent download button.

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

app/Notifications/TransferRecipientNotification.php

@@ -24,7 +24,7 @@ class TransferRecipientNotification extends Notification
     public function toMail(mixed $notifiable): MailMessage
     {
         $transfer = $this->transfer->loadMissing(['files', 'qrCode', 'user']);
-        $publicUrl = $transfer->qrCode?->publicUrl() ?? '';
+        $publicUrl = $transfer->qrCode?->shareUrl() ?? '';
 
         return (new MailMessage())
             ->subject($this->subjectLine())