High contrast mode system for improved visual accessibility in Raxol terminals.

This module provides comprehensive high contrast support including:

• Multiple high contrast themes (black/white, white/black, custom)
• WCAG 2.1 AA and AAA contrast ratio compliance
• Automatic contrast adjustment for different lighting conditions
• Color blindness accommodation (Deuteranopia, Protanopia, Tritanopia)
• Large text mode with scalable fonts
• Custom user-defined contrast schemes
• System integration with OS accessibility settings
• Dynamic contrast adjustment based on ambient light
• Color palette optimization for terminal interfaces

Features

Contrast Modes

• High Contrast Black (white text on black background)
• High Contrast White (black text on white background)
• High Contrast Custom (user-defined color schemes)
• Inverted Colors mode
• Grayscale mode with enhanced contrast
• Adaptive contrast based on content type

Accessibility Compliance

• WCAG 2.1 Level AA (4.5:1 contrast ratio)
• WCAG 2.1 Level AAA (7:1 contrast ratio)
• Color blindness simulation and correction
• Focus indicator enhancement
• Text shadow and outline options for improved readability

Usage

# Initialize high contrast system
{:ok, hc} = HighContrast.start_link(
  default_theme: :high_contrast_black,
  compliance_level: :wcag_aa,
  auto_detect_system: true,
  color_blind_support: true
)

# Apply high contrast theme
HighContrast.apply_theme(hc, :high_contrast_white)

# Create custom theme with WCAG compliance
custom_theme = %{
  name: "custom_blue",
  background: {0, 0, 51},      # Dark blue
  foreground: {255, 255, 204}, # Light yellow
  accent: {255, 102, 0},       # Orange
  compliance_level: :wcag_aaa
}
HighContrast.register_theme(hc, custom_theme)

# Enable color blindness accommodation
HighContrast.configure_color_blindness(hc, :deuteranopia, %{
  strength: 0.8,
  enable_patterns: true,
  alternative_indicators: [:shapes, :textures]
})