docs: replace emoji icons with official brand SVG logos

Download official brand logos from SimpleIcons CDN for all servers:
GitHub, Atlassian, Cloudflare, PostgreSQL, Azure DevOps, Filesystem,
Slack, Stripe, Linear, Sentry, Notion, Datadog, MongoDB, Puppeteer.
Inject logos via Playwright after React render, properly sized for
both Servers page (40px) and Discover card grid (30px).

https://claude.ai/code/session_01W32JdTpYeN92qNrHPgMyVo

Author: claude