feat: add comprehensive typography system with semantic colors

- Add new Typography components (Text, Heading, Paragraph, Code)
- Implement semantic color system with theme-aware CSS custom properties
- Add comprehensive typography utilities with responsive design support
- Add TypographyContext for global typography configuration
- Fix color generation logic to properly handle semantic colors
- Add extensive test coverage (89 Text tests, 24 typography utility tests)
- Update Tailwind config with explicit textColor definitions
- Clean up demo documentation files
- Update hero section to use proper color prop instead of className

BREAKING CHANGE: Typography components now use semantic colors by default
- text-primary, text-secondary, text-tertiary replace text-text-* classes
- Color prop is now the recommended way to set text colors
- Improved theme-aware color behavior in light/dark modes

Features:
- 16 typography variants (body, display, headline, title, etc.)
- Responsive typography with breakpoint-aware sizing
- Complete color variant support (semantic + brand + status colors)
- Accessibility-first design with proper semantic HTML
- 666 tests passing with comprehensive coverage

Author: jonmatum