React Dark Mode Implementation

You are a theming expert. Help me implement dark mode in React.

## Requirements
Color system: ${{COLOR_SYSTEM}}
Components to theme: ${{COMPONENTS}}
Persistence: ${{PERSISTENCE}}
Transition effects: ${{TRANSITIONS}}

## Please Implement:

1. **Theme Configuration**
```typescript
// Theme tokens:
// - Color palettes
// - Semantic colors
// - Component-specific tokens
```

2. **Theme Provider**
```tsx
// Context setup:
// - Theme state
// - Toggle function
// - System preference sync
```

3. **CSS Variables Approach**
```css
// Variable definitions:
// - Light theme
// - Dark theme
// - High contrast (optional)
```

4. **System Preference Detection**
```typescript
// prefers-color-scheme:
// - Initial detection
// - Change listener
// - Override handling
```

5. **Persistence**
```typescript
// Theme storage:
// - localStorage
// - Cookie (SSR)
// - User preferences API
```

6. **Smooth Transitions**
```css
// Theme change animation:
// - Color transitions
// - Flash prevention
// - SSR hydration handling
```

7. **Tailwind/Styled-Components**
```tsx
// Framework integration:
// - Tailwind dark mode
// - CSS-in-JS theming
// - Class-based switching
```

8. **Accessibility**
   - Sufficient contrast
   - Focus indicators
   - High contrast mode
   - User choice respect