feat: implement UI redesign for Comparador de Notas

- Introduced a new theme for the application based on dark navy aesthetics.
- Created design tokens for colors, spacings, and border radii.
- Developed a theme module in Rust to manage styles for various UI components.
- Updated multiple screens and components to align with the new design, including cards, buttons, badges, and progress bars.
- Enhanced user experience with improved layouts and visual elements across the application.

src/main.rs

@@ -9,6 +9,7 @@ use ui::app::App;
 
 fn main() -> iced::Result {
     iced::application("Comparador de Notas", App::update, App::view)
+        .theme(|_app| ui::theme::tema_dark())
         .window(iced::window::Settings {
             size: iced::Size::new(1024.0, 768.0),
             min_size: Some(iced::Size::new(800.0, 600.0)),