[FEATURE] Add High Contrast Mode for Enhanced Accessibility

Is your feature request related to a problem? Please describe.

Users with visual impairments or those working in high-glare environments may struggle with the current color scheme. The app currently lacks accessibility options for users who need higher contrast ratios for better readability.

Describe the solution you'd like

Add a high contrast mode that:

• Implements WCAG 2.1 Level AAA contrast ratios (7:1 for normal text, 4.5:1 for large text)
• Adds a toggle button in the UI header next to the existing controls
• Persists the user's preference in local storage
• Modifies the ui configuration in app/app.config.ts to support an alternative high-contrast color scheme
• Updates all Nuxt UI components to respect the high contrast setting

Describe alternatives you've considered

1. Browser-level high contrast mode support only
2. CSS custom properties override without a dedicated mode
3. Multiple color themes instead of just high contrast

Additional context

This feature should integrate with the existing color system defined in app/app.config.ts and work seamlessly with the current Nuxt UI components. The implementation should follow the component structure in app/components/.