[Design]: Create Design Tokens (Light & Dark Mode)

[Anglehr]

Title: Design Tokens: Light & Dark Mode

Description:

Create a complete set of design tokens to support both light and dark themes.

Tasks:

Define color tokens (background, text, borders, states)
Create light mode token set
Create dark mode token set
Ensure accessibility (contrast compliance)
Export tokens for dev use (JSON / CSS variables)

Acceptance Criteria:

Tokens available for both themes
Meets accessibility standards
Easily consumable by frontend