Bug: aggregated mail attachment merge references literal 'id' key

[somethingwithproof]

Summary

In notification queue mail aggregation, attachment merge uses $emails['id']['attachments'] instead of $emails[$id]['attachments'].

Impact

• Existing attachments for the current aggregation bucket may be skipped/lost.
• Can trigger undefined-index notices depending on runtime settings.

Location

• thold_functions.php, notification queue processing branch near:

$emails[$id]['attachments'] += array_merge($emails['id']['attachments'], $attachments);

Expected

Use the computed $id bucket and a proper merge strategy for attachment arrays.