Glossary, FAQ hub, changelog, and 5 new topic pages

New /glossary (DefinedTermSet), /faq hub, /changelog, and 5 new topic pages: AI for healthcare, AI for managers, AI job hunting, AI video generation, AI learning app for beginners. New machine-readable feeds: /iro.json, /manifest.json, /opensearch.xml, /humans.txt, /.well-known/security.txt. Markdown mirrors under /llms/.