Make primary CTA of My Books Dropper "Add to List" when logged out

[mekarpeles]

Closes #11496

Reduce confusion for patrons who click "Want to Read" expecting to get the book (for logged out patrons)

This pull request makes a small improvement to the logic for displaying the primary action message in the primary_action.html template. Now, if there is no read_status and the user is not logged in (user_key is not set), the message will show as "Add to List" instead of "Want to Read". This clarifies the action for anonymous users.

[Copilot]

Pull Request Overview

This PR improves the user experience for logged-out visitors by changing the primary CTA button text from "Want to Read" to "Add to List" when no reading status is set and the user is not authenticated. This reduces confusion for anonymous users who might misinterpret "Want to Read" as a way to access the book content.

Key changes:

• Modified the conditional logic in primary_action.html to check for user_key before defaulting to "Want to Read"
• Added "Add to List" as the message for logged-out users without a reading status

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[jimchamp]

Works as expected on search result pages, book pages, and author pages.