RichText: honor a link's newTab field

The link/autolink converters never read node.fields.newTab, so setting
"open in new tab" on a link in the Payload editor had no effect.
Needed now that the Die Sieben post's template-download link opens a
PNG in-place instead of navigating away from the article.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013Eg6h91yngXmSnM51wxXM8

app/components/RichText.tsx

@@ -176,7 +176,11 @@ function buildConverters(quoteLabel: string): JSXConvertersFunction {
     },
     listitem: ({ node, nodesToJSX }) => <li>{nodesToJSX({ nodes: node.children })}</li>,
     link: ({ node, nodesToJSX }) => (
-      <a href={node.fields?.url ?? "#"} className="text-brand hover:underline">
+      <a
+        href={node.fields?.url ?? "#"}
+        className="text-brand hover:underline"
+        {...(node.fields?.newTab ? { target: "_blank", rel: "noopener noreferrer" } : {})}
+      >
         {nodesToJSX({ nodes: node.children })}
       </a>
     ),