Fix author merge HTML entity rendering (#10640)

[FizaSiddique123]

Closes #10640

fix

Technical

This PR improves author merge handling by ensuring HTML entities are properly preserved and rendered.

Changes include:

• Updating merge_author in openlibrary/plugins/upstream/utils.py to correctly handle HTML entities.
• Updating openlibrary/templates/merge/authors.html to safely display HTML entity-encoded fields during merges.

Testing

1. Attempt to merge two author records containing HTML entities (e.g., &, ", ').
2. Verify the merged output keeps entity encoding intact.
3. Confirm the updated template displays encoded values correctly.

Screenshot

N/A — no direct UI redesign; only correct rendering behavior.

Stakeholders

@openlibrary/issues @internetarchive/openlibrary-maintainers