Implement Light/Dark Theme Support

[pbalduino]

Description

Add theme switching capability for stage musicians who prefer dark screens

Priority

🟡 Medium

Category

Theming

Details

• Implement ThemeMode support in Flutter app
• Create dark theme variant matching current design language
• Add theme toggle in settings screen
• Ensure all screens work properly in both themes
• Save theme preference to local storage

Files Affected

• lib/main.dart
• lib/app.dart
• lib/screens/settings_screen.dart
• lib/screens/tuner_screen.dart

Acceptance Criteria

• App supports both light and dark themes
• Theme can be toggled from settings
• All UI elements are properly themed
• Theme preference persists between app restarts
• Dark theme is suitable for stage use

Task ID: THEME-001

[pbalduino]

Light/Dark Theme Support Implementation Complete

Successfully implemented comprehensive theme switching capability for enhanced accessibility and stage performance:

✅ Theme System: Full ThemeMode support with light and dark variants
✅ Design Language: Dark theme maintains current design aesthetic
✅ Smart Colors: Dynamic color adaptation based on theme context
✅ Accessibility: Proper contrast ratios and color schemes
✅ User Preference: Theme selection persists between app sessions

Technical Implementation:

• Created AppTheme system with comprehensive theme definitions
• Added theme-aware color extensions (theme.overlayOnBackground, theme.tunerBackgroundGradient)
• Dynamic color calculations for backgrounds, borders, and text
• Proper Material Design color scheme integration
• Theme-aware debug overlay and UI components

Enhanced Features:

• Stage Performance: Dark theme optimized for low-light environments
• Battery Efficiency: Dark theme reduces screen power consumption on OLED displays
• Visual Comfort: Reduced eye strain in dark environments
• Professional Appearance: Maintains elegant design across both themes

User Experience:
Stage musicians can now switch to dark theme for optimal visibility during performances, while maintaining the app's beautiful design language and accessibility standards.