✨ Complete UI overhaul with Archipelago Blue theme and custom branding

📝 Summary:
Major visual improvements including unique theme colors, fixed icons, custom
launcher icons, in-app logo integration, and improved map UX. All 289 tests
pass with full WCAG AA+ accessibility compliance.

🔧 Changes:
- 🎨 Implement "Archipelago Blue" theme (teal #006064 + orange #FF6F00)
- 🐛 Fix onboarding icons by adding explicit container colors
- 🖼️ Replace Android launcher icons with custom PH Fare Calculator logo
- 🏠 Add app logo to Settings screen About section
- 🗺️ Increase initial map preview size by 40% (200px → 280px)
- 📚 Add comprehensive color theme research documentation
- 📋 Create theme specification design document

📁 Files Changed:
- lib/src/core/theme/app_theme.dart (theme colors)
- lib/src/presentation/screens/main_screen.dart (map sizing)
- lib/src/presentation/screens/settings_screen.dart (logo integration)
- android/app/src/main/res/mipmap-*/ic_launcher.png (5 density sizes)
- assets/icons/PHFareCalculatorLogo/ (logo assets)
- docs/design/theme_specification.md (design spec)
- docs/research/color_theme_research_2024_2025.md (research)

✅ Verification:
- All 289 tests pass
- No analyzer issues
- WCAG AA+ accessibility compliant

Author: MasuRii