fix #3440556: Add field for the name of the person signing.

Closes #3440556

While implementing this feature, I noticed a couple of related enhancements that could be useful in the future. I’ve added them here for consideration. These are not included in the current scope to keep this change focused, but we can consider them as separate improvements later.

1. Auto-fill signer name for logged-in users

2. Audit trail (who signed, when, from where)