fix: use pinned property for featuredPosts collection

Renamed from "featured" to "pinned" to avoid conflict with the
"featured" hero image property in MF2/Micropub. Handles both boolean
and string "true" values from YAML frontmatter.

Confab-Link: http://localhost:8080/sessions/bd3f7012-c703-47e9-bfe2-2ad04ce1842d

eleventy.config.js

@@ -856,12 +856,13 @@ export default function (eleventyConfig) {
       .slice(0, 5);
   });
 
-  // Featured posts — curated selection via `featured: true` frontmatter
+  // Featured posts — curated selection via `pinned: true` frontmatter
+  // Property named "pinned" to avoid conflict with "featured" (hero image) in MF2/Micropub
   eleventyConfig.addCollection("featuredPosts", function (collectionApi) {
     return collectionApi
       .getFilteredByGlob("content/**/*.md")
       .filter(isPublished)
-      .filter((item) => item.data.featured === true)
+      .filter((item) => item.data.pinned === true || item.data.pinned === "true")
       .sort((a, b) => b.date - a.date);
   });