[codex] Refresh DosCode marketing copy and AI metadata

[Vladib80]

Summary

• Restore the pulled GitHub visual design while refreshing homepage marketing copy in Russian, English, and Kazakh
• Add product marketing context for future copy work
• Expand AI/SEO metadata with richer schema, llms.txt, robots.txt AI crawler rules, and agent-map alignment

Validation

• npm run build
• Locale JSON parse checks
• Generated JSON-LD checks for /, /en/, and /kk/
• Playwright screenshots for RU desktop/mobile, EN, and KK