[A11Y] Cover issue link must have discernible text

[israelcefrin]

Issue Description

Some issues present cover with a link, but there is no text to be announced by screenreaders.

How to reproduce / Current behavior

1. Activate Pragma theme
2. Add a cover to a published issue and leave empty the alternative text field.
3. Go to the Archives page on the frontend
4. Using a screenreader, navigate to the cover
5. See the error

What application are you using?

OJS version 3.4

Stack used

• Device: Laptop
• OS: MacOS
• Browser: Chrome
• Version: 130.0

Testing method

• Method: (e.g. Manual; Keyboard)
• Automated test: (e.g. tool name)

Action

If this is only a decorative image, remove the hyperlink from the image and add an empty alt attribute to indicate this is a decorative image.
If the image must to be announced, it should require the alternative text in the backend.

Additional information