feat: refactor theme, add tailwind-scrollbar, and improve UI components

- Removed manual theme switching logic and ThemeProvider
- Installed and configured tailwind-scrollbar plugin
- Updated FileConverter and ConversionOptions to use shadcn Input
- Refactored FontSelector to use shadcn Tabs
- Simplified global styles and adjusted glassmorphic effects

components/ToolCard.tsx

@@ -31,12 +31,12 @@ export default function ToolCard({ title, description, icon, url, gradient, acce
       <div className="glass relative overflow-hidden rounded-2xl p-8 h-full transition-all duration-300 group-hover:shadow-2xl group-hover:bg-card/80">
         {/* Gradient overlay on hover */}
         <div
-          className={`absolute inset-0 opacity-0 group-hover:opacity-10 dark:group-hover:opacity-15 transition-opacity duration-300 ${gradient}`}
+          className={`absolute inset-0 opacity-0 group-hover:opacity-15 transition-opacity duration-300 ${gradient}`}
         />
 
         {/* Glow effect */}
         <div className="absolute inset-0 opacity-0 group-hover:opacity-100 transition-opacity duration-300 blur-xl -z-10">
-          <div className={`w-full h-full ${gradient} opacity-20 dark:opacity-30`} />
+          <div className={`w-full h-full ${gradient} opacity-30`} />
         </div>
 
         {/* Icon */}