main
feat(simulator): simulator page with EthicalSimulator, nav link
fix(i18n): 404 page fully uses t() and typed Lang
feat: Astro 5 migration — full EN translations, modern design, interactivity
feat: scientific foundations appendix (RU+EN), sitemap.xml, RSS feed, PWA manifest
feat(seo): add hreflang to sitemap, add contact+simulator pages