feat: migrate blog FAQs to reusable MDX accordion

- add Astro MDX support and convert FAQ-bearing posts to MDX
- centralize FAQ markup, scoped styling, behavior, and JSON-LD
- preserve FAQ content and links across English and Spanish posts
- extend blog audits and document the MDX editing workflow
- remove obsolete global FAQ styles
- ignore Front Matter CMS generated state

www/package.json

@@ -20,6 +20,7 @@
     "generate:redirects": "node tools/generate-redirects.mjs"
   },
   "dependencies": {
+    "@astrojs/mdx": "^4.3.14",
     "astro": "^5.10.0",
     "cheerio": "^1.1.0",
     "fast-glob": "^3.3.3",