#1083 Render italics and small caps in publication titles on cluster pages

Publication titles on the cluster pages showed literal markup from Crossref, such as Promoting Research Integrity in <scp>A</scp>frica and Celebrating 30 years of <i>Feminism &amp; Psychology</i>. This PR renders that markup instead of stripping it.

• Allow-list: a new partial, layouts/partials/clusters/rich_text.html, decodes entities and escapes the title. It then restores only <i>/<em> (as <i>) and <scp>, which becomes <span class="scp"> set in small caps. All other markup stays escaped text.
• Where it applies: the recommended and compact cards in cluster_section.html and featured_cards.html.
• static/js/featured-resources.js: the same rule (richText) applies to the reference popup and to reading-list titles and APA references. Copy-APA and the PDF export use plain text (plainText). Entities in APA references now show as & rather than &.
• CSS: .scp{font-variant:small-caps} is added. Card, popup and reading-list titles and APA references join the D15 exception that allows true italics in reference lists. In titles, the italic words keep the title's weight, but Doors has only a 400 italic face, so they render lighter.
• Data still to come: titles with run-together words in Crossref ("Let's PublishFewerPapers") were fixed in the Publications sheet. The generator side of the cleanup is in #1077, into main. Both arrive with the next data-processing run, and the templates work with the current data too.

Checks

• hugo --gc --minify builds, the unit tests pass, and check_seo_html.py passes. New check 17 fails if cluster pages show literal <i>/<em>/<scp> markup.
• The built cluster pages contain no <i>, <scp, <em or &.
• Cluster pages were checked in Chrome:
  • Cluster 3: small caps show in the card, the popup title and the APA reference.
  • Cluster 4: italics show in a card title.
  • Cluster 10: italics show in a popup APA reference.

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