Fix: Show covers in search results using edition fallback (Fixes #11563)

[FizaSiddique123]

What issue does this PR close?

Closes #11563

What does this PR achieve?

This PR fixes an issue where some search results failed to display a cover image even though the corresponding work/edition page showed one.

The previous logic only attempted get_cover_url(selected_ed).
However, many Solr search documents do not include cover_i, and therefore get_cover_url returned None, resulting in missing covers.

This PR adds proper fallback logic so search results can display covers whenever a book has any valid cover available.

Technical

Updated SearchResultsWork.html to include fallback cover logic:

1. Try get_cover_url(selected_ed)
2. If missing, try:
   • cover_i
   • cover_edition_key
   • first edition_key
3. If all fail, use default placeholder icon

This mirrors other areas of OpenLibrary where fallback logic is used, ensuring that search results behave consistently.

Testing

To reproduce:

1. Go to
   /search?q=Goa+Stott&mode=everything&sort=old&first_publish_year=2011

2. Before this PR:
   The result “Goa / Stott” displays no cover in search results.

3. After this PR:
   The cover image appears correctly by using edition fallbacks.

Stakeholders

@internetarchive/openlibrary-developers

[FizaSiddique123]

Hi! This PR is ready for review.
Please let me know if any changes are needed. Thank you!