fix(design): improve OG image text readability for social previews (#137)

## Summary

- Tagline font size: 26px → 32px (split to two lines to fit the 1200px
canvas width)
- "INTERNET COMPUTER" eyebrow: 15px → 19px

Both were effectively illegible at the ~600px width social platforms
(Twitter, LinkedIn, Slack) use to render OG preview images.

## Sync recommendation

hand-written

Author: marc0olo