refactor: Migrate from tailwind.js config to Tailwind CSS config (#451)

* refactor: Migrate from tailwind.js config to Tailwind CSS configuration and improve component styling

- Removed extensive theme and animation configurations from tailwind.config.js, migrating them to index.css for better organization.
- Updated components to utilize CSS variables for grid layouts and animations, enhancing maintainability.
- Adjusted various components to reflect the new CSS structure, ensuring consistent styling across the application.
- Improved accessibility and responsiveness in several UI components, including headers and popovers.
- Fixed minor styling issues and optimized class usage for better performance.

* style: use default tailwindcss/forms options

* refactor(Header): remove unused LuUser icon import

ui/src/components/popovers/PasteModal.tsx

@@ -74,7 +74,7 @@ export default function PasteModal() {
   return (
     <GridCard>
       <div className="space-y-4 p-4 py-3">
-        <div className="grid h-full grid-rows-headerBody">
+        <div className="grid h-full grid-rows-(--grid-headerBody)">
           <div className="h-full space-y-4">
             <div className="space-y-4">
               <SettingsPageHeader