chore: remove avenir and fakt pro font

[amberkamboj77]

Description

This PR removes all proprietary fonts (Avenir, Fakt Pro) from the styleguide packages and replaces them with Inter, an open-source font (SIL Open Font License), along with system font fallbacks.

Changes:

Core package: Replaced Fakt Pro font with Inter + system font fallbacks in typography definitions
Components package: Updated to use local core paths instead of npm dependency, added Inter font files
React-components package: Updated to use local core paths instead of npm dependency
Email templates: Use system font stack (no web fonts)

New font stack:

'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif

Version bumps:

styleguide-core: 3.0.0 → 3.1.0
styleguide-components: 2.0.10 → 3.1.0
styleguide-react-components: 1.0.4 → 1.0.5

References

Inter font: https://rsms.me/inter/ (SIL Open Font License 1.1)

Testing

Core
cd packages/core && npm install && npm run build && npx gulp cdn
grep -i "fakt|avenir" cdn/*.css # Returns nothing

Components
cd packages/components && npm install && npm run build && npx gulp cdn
grep -i "fakt|avenir" cdn/*.css # Returns nothing

React-components
cd packages/react-components && npm install && npm run build:css
grep -i "fakt|avenir" build/*.css # Returns nothing

• All packages build successfully (npm run build)
• CDN preparation works (npx gulp cdn)
• Verified no fakt or avenir references in built CSS files
• Tested with Node.js v22.16.0

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not the default branch