feat: Upgrade to Tailwind CSS v4.1.18

- Migrate from tailwindcss v3.3 to v4.1.18
- Replace @tailwind directives with @import 'tailwindcss'
- Move custom colors to @theme block in globals.css
- Convert custom utilities to @utility syntax
- Update PostCSS config to use @tailwindcss/postcss
- Remove autoprefixer (now built-in)

src/components/BottleSkeletonCard.tsx

@@ -32,7 +32,7 @@ export default function BottleSkeletonCard({
                 }`}
         >
             {/* Image */}
-            <div className="aspect-[3/4] bg-zinc-950 relative overflow-hidden">
+            <div className="aspect-3/4 bg-zinc-950 relative overflow-hidden">
                 {imageUrl ? (
                     <img
                         src={imageUrl}
@@ -81,12 +81,12 @@ export default function BottleSkeletonCard({
             {/* Info */}
             <div className="p-3">
                 {/* Skeleton Name */}
-                <div className="h-4 bg-zinc-800 rounded animate-pulse mb-2 w-3/4" />
+                <div className="h-4 bg-zinc-800 rounded-sm animate-pulse mb-2 w-3/4" />
 
                 {/* Skeleton Details */}
                 <div className="flex gap-2">
-                    <div className="h-3 bg-zinc-800/50 rounded animate-pulse w-12" />
-                    <div className="h-3 bg-zinc-800/50 rounded animate-pulse w-8" />
+                    <div className="h-3 bg-zinc-800/50 rounded-sm animate-pulse w-12" />
+                    <div className="h-3 bg-zinc-800/50 rounded-sm animate-pulse w-8" />
                 </div>
             </div>
         </motion.div>