Deploy: worker improvements, markdown serving, and tests

[MarketDataApp]

Summary

• Markdown serving: Worker serves clean markdown for .md URLs and Accept: text/markdown header — strips frontmatter, imports, converts MDX components to headings
• SDK PHP redirect: /docs/sdk-php/* → GitHub Pages with doubled directory fix
• 404 logging: Worker logs 404 paths/referers to Cloudflare Workers Logs (filterable by level = 404)
• Worker tests: 30 unit tests + 162 integration tests (vitest), CI runs unit tests before deploy
• Misc fixes: robots.txt blocking, feed→mode redirect, sidebar custom props migration, editUrl points to self-hosted .md

Test plan

• Verify www.marketdata.app/docs/api/options/chain.md returns clean markdown
• Verify Accept: text/markdown header returns markdown on any docs page
• Verify /docs/sdk-php/classes/MarketDataApp-Enums-Range.html redirects to GitHub Pages
• Verify /docs/api/universal-parameters/feed redirects to /mode
• Check Cloudflare Workers Logs for 404 entries
• cd worker && yarn test passes