[BUG] Certificate Signature Not Displayed in Preview For Honor Seat

[abdullah8590]

When a user creates an Honor Seat for a course and sets up a certificate with all required information, including adding a signature, the signature does not appear on the certificate preview.

Steps to Reproduce:

1. Create an Honor Seat for a course, django -> course modes

2. Create a certificate for the same course.

3. Add all certificate details (Course title override, Name, Title, signature image).

4. Save the certificate.

5. Click on Preview Certificate.

Expected Result:
The signature should be visible on the certificate preview as configured.

Actual Result:
The signature does not appear in the certificate preview, even though it has been added and saved.