Add media pesata page and corresponding styles

- Created a new page for calculating weighted averages and graduation votes (`media-pesata.astro`) with a layout and introductory text.
- Implemented a script to initialize the media pesata application.
- Added CSS styles for the media pesata page and its components.
- Updated existing media page (`media.astro`) to include similar structure and functionality.
- Introduced error handling for the application initialization script.
- Established a comprehensive CSS file for the media pesata application, including styles for various UI elements and responsive design.

src/components/Header.astro

@@ -6,6 +6,7 @@ const links = [
     { href: '/notizie', text: 'Notizie' },
     { href: '/guide', text: 'Guide' },
     { href: '/domande-esami', text: 'Domande Orali' },
+    // { href: '/media-pesata', text: 'Media Pesata' }, // Beta testing - solo URL diretto
     { href: '/storia', text: 'Storia' },
     // { href: '/login', text: 'Login' },
 ]