feat: upgrade to tailwindcss v4

vite.config.ts

@@ -1,8 +1,7 @@
 import { readFile } from 'node:fs/promises';
 import { reactRouter } from '@react-router/dev/vite';
-import autoprefixer from 'autoprefixer';
+import tailwindcss from '@tailwindcss/vite';
 import { reactRouterHonoServer } from 'react-router-hono-server/dev';
-import tailwindcss from 'tailwindcss';
 import { defineConfig } from 'vite';
 import tsconfigPaths from 'vite-tsconfig-paths';
 import { parse } from 'yaml';
@@ -25,16 +24,16 @@ const { server } = parse(config);
 
 export default defineConfig(({ isSsrBuild }) => ({
 	base: isSsrBuild ? `${prefix}/` : undefined,
-	plugins: [reactRouterHonoServer(), reactRouter(), tsconfigPaths()],
+	plugins: [
+		reactRouterHonoServer(),
+		reactRouter(),
+		tailwindcss(),
+		tsconfigPaths(),
+	],
 	server: {
 		host: server.host,
 		port: server.port,
 	},
-	css: {
-		postcss: {
-			plugins: [tailwindcss, autoprefixer],
-		},
-	},
 	ssr: {
 		target: 'node',
 		noExternal: isSsrBuild ? true : undefined,