feat: Add 6 new modern themes to calculator

[linols]

🎨 New Themes Added

This PR adds 6 new modern and visually appealing themes to the calculator, expanding the existing theme collection.
issue : Novos temas para a Calculadora Tk #2

✨ New Themes

• ** Forest** - Natural green tones with forest-inspired colors
• ** Sunset** - Warm orange and brown palette for a cozy feel
• ** Cyber** - Cyberpunk style with neon green on black background
• ** Rose Gold** - Elegant rose gold with purple accents
• ** Mint Fresh** - Fresh mint green with turquoise highlights
• ** Midnight Blue** - Deep midnight blue with light blue accents
• ** Warm Orange** - Energetic orange theme with warm tones

🔧 Technical Details

• All themes follow the existing JSON structure in app/settings/settings.json
• Each theme includes proper color contrast for accessibility
• Interactive button states (hover effects) are implemented
• Themes are fully compatible with the existing theme system
• No breaking changes to existing functionality

🎯 Features

• 7 new themes added to the existing collection
• Modern color palettes with carefully selected colors
• Consistent design language across all themes
• Easy theme switching through the existing menu system
• Automatic theme persistence - selected theme is saved

🧪 Testing

• ✅ All themes load correctly
• ✅ Theme switching works as expected
• ✅ Color contrast is optimal for readability
• ✅ Interactive states work properly
• ✅ No conflicts with existing themes

📸 Preview

The new themes provide a diverse range of visual styles:

• Nature lovers: Forest, Mint Fresh
• Tech enthusiasts: Cyber, Midnight Blue
• Elegant users: Rose Gold, Warm Orange
• Warm vibes: Sunset, Warm Orange

How to Use

1. Launch the calculator
2. Go to "Configuração" → "Tema"
3. Select your preferred theme from the expanded list
4. The application will restart with the new theme applied