Add dark/light theme toggle

[Mosas2000]

Support both themes:

• Theme switcher in settings
• Persist preference
• Smooth transition between themes

[Yusufolosun]

Hi @Mosas2000! 👋

I'd love to work on this issue and implement dark/light theme support for 0xCast.

Proposed Approach:

• Configure Tailwind's dark mode with class-based toggle
• Create a ThemeContext with React for global state management
• Build a theme switcher component for the settings
• Implement localStorage persistence
• Add smooth CSS transitions between themes

I'm familiar with React, TypeScript, and Tailwind CSS. I've reviewed the frontend structure and I'm ready to get started!

Let me know if this approach sounds good or if you have any specific preferences for the implementation.

Thanks!