Simplify recipient emails and add live upload progress on create.

Recipients always get the download link immediately when an email is set.
Large files upload in the background with per-file and overall progress bars.

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

config/transfer.php

@@ -29,17 +29,6 @@ return [
     // Days to keep files after a failed renewal before automatic deletion.
     'grace_period_days' => (int) env('TRANSFER_GRACE_PERIOD_DAYS', 15),
 
-    // Recipient email milestones (checkboxes on the create transfer form).
-    'recipient_email_milestones' => [
-        'created' => 'Send download link immediately',
-        '7' => '7 days before files become unavailable',
-        '3' => '3 days before files become unavailable',
-        '1' => '1 day before files become unavailable',
-        'grace' => 'When files enter the payment grace period',
-    ],
-
-    'default_recipient_email_milestones' => ['created'],
-
     // Owner emails when a transfer enters grace and before files are deleted.
     'owner_grace_email_milestones' => ['grace_entered', '7', '3', '1'],