enh: Adjust colors, cards, and decoration in theme

[Wuyika]

Description

• Used apptones in appthemes for design consistency across the app.

Light Theme	Dark Theme

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[sourceant]

Code Review Summary

This PR implements a design refresh by introducing a more structured theme system (AppTones) and improving UI components like cards and background decorations.

🚀 Key Improvements

• Centralized theme management in lib/presentation/utils/theme.dart.
• Standardized background colors across main screens using tones.bgPage.
• Added brand-consistent background decorations via IconBackgroundDecor.

💡 Minor Suggestions

• Fix minor spacing in AppTheme definition.
• Verify text contrast on primary buttons in dark mode.

[sourceant]

Review complete. See the overview comment for a summary.

[sourceant]

Review complete. See the overview comment for a summary.

[sourceant]

Review complete. See the overview comment for a summary.