feat(add-theme): #ENABLING-653 add new theme neov2

[pascalsaussier-edifice]

Description

This pull request introduces the new neov2 theme, built upon a modernized theming architecture in the bootstrap package. This new architecture leverages Sass maps and CSS variables to provide a more flexible and maintainable approach to theme development.

Key changes include:

• A new _theme-api.scss module defining a contract for themes based on configuration maps.
• The neov2 theme configuration, including its initial color palette and typography, is defined in configs/_neov2.scss.
• Icon color definitions have been refactored, moving from a single global _icons.scss abstract to theme-specific files (themes/neo/_icons.scss, themes/one/_icons.scss, themes/neov2/_icons.scss). The icon token generation (tokens/_icons.scss) now dynamically uses these theme-specific maps.
• The neov2 theme structure supports component-level overrides, as demonstrated by the new overrides/ directory.
• Comprehensive documentation (migration strategy, overrides inventory, theming guide) is included for neov2 to guide future theme development and migration efforts.
• The neov2 theme is integrated into Storybook, allowing for easy preview and testing.
• A minor update in packages/react/src/hooks/useBrowserInfo/useBrowserInfo.ts changes the import style for UAParser.

This initiative, related to #ENABLING-653, lays the groundwork for a progressive migration to a more robust and scalable theming system.

Which Package changed?

• Components
• Core
• Icons
• Hooks

Has the documentation changed?

• Storybook

Type of change

Please check options that are relevant.

• Chore (PATCH)
• Doc (PATCH)
• Bug fix (PATCH)
• New feature (MINOR)
• Breaking change (MAJOR)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings