Design: setup core design tokens

[urmauur]

Implement design tokens for consistent theming across the UI library. Tokens should be defined in :root CSS variables and able to use for Figma for designers.
Create foundational UI components that use tokens and follow accessibility best practices.

Foundation

• Colors
• Typography
• Spacing
• Elevation
• Iconography

Core Components

• Button (variants + sizes + icons)
• Input (text field, password, with label & error state)
• Textarea
• Select / Dropdown
• Checkbox
• Radio group
• Switch / Toggle
• Card (with shadow & radius tokens)

Theme

• All component should work with dynamic theme

Documentation

• Setup Documentation for Design System