feat: Replace ProximaNova with Figtree font family

[mateusz-zaboj]

🎨 Overview

This PR replaces the ProximaNova font family with Figtree across the entire Brainly Style Guide design system.

📋 Changes Made

Font Assets

• ✅ Added Figtree-*.woff* files with accordingly as it was done with ProximaNova
• ✅ Updated both .storybook/public/fonts/ and src/fonts/ directories
• ✅ Added Figtree Regular, Bold, and Black variants
• ✅ ProximaNova was not removed from the repository, to allow being hosted for older versions of SG

Code Changes

• ✅ SCSS: Updated $fontFamilyProximaNova variable in src/sass/_config.scss
• ✅ Fonts: Modified @font-face declarations in src/sass/_fonts.scss
• ✅ CSS: Updated font stack in src/css/config/fontFamily.js

Compatibility

• ✅ Preserved existing CSS classes and styling hooks
• ✅ No breaking changes to JavaScript/TypeScript interfaces

🔍 Testing Instructions

# Install dependencies
yarn install

# Build the project
yarn build

# Start Storybook to verify font rendering
yarn storybook

# Run tests to ensure no regressions
yarn test

Visual Verification:

• Check all text components render with Figtree font
• Verify font weights (Regular 400, Bold 700, Black 900) display correctly

🎯 Impact

• Visual Change: All text in the design system will use Figtree instead of ProximaNova
• Performance: Figtree has similar file sizes and web font performance

✅ Checklist

• Font files properly converted to WOFF/WOFF2 format
• SCSS variables updated correctly
• CSS configuration modified
• Build process completes without errors
• Storybook renders with new font
• All tests pass

Demo with live comparison Proxima and Figtree change (enable voice):

Proxima_to_Figtree_comparison.mov

[mateusz-zaboj]

I checked that after font change and now with Figtree we don't need additional top: 1px.

[mateusz-zaboj]

I decided to remove that paragraph since it's not relevant for now.

[mateusz-zaboj]

With @matzimowski we decided to not remove ProximaNova assets in that PR. In the first place, we want to replace Proxima usage in our codebase and then as the last step we will remove ProximaNova assets from brainly-style-guide.