Website overhaul: clean file structure, rewrite copy, add footer and 404

- Delete root-level duplicate HTML/CSS/favicon (served from docs/)
- Move robots.txt, sitemap.xml, llms.txt, llms-full.txt into docs/
- Move internal strategy docs to docs-internal/
- Remove old downloads/ folder (~35 MB of archived zips)
- Rewrite all user-facing copy: kill AI slop, developer jargon, SEO scaffolding
- Add footer to all 4 pages
- Replace redirect-only 404 with a styled page
- Add FAQ hover transitions
- Update sitemap lastmod dates

Author: offyotto