refactor: remove @nuxt/ui integration and update Vite configuration

- Removed @nuxt/ui plugin from main.ts and index.css
- Updated vite.config.ts to replace @nuxt/ui with unplugin-auto-import and unplugin-vue-components for better component auto-importing and resolution

src/theme/index.css

@@ -1,2 +1 @@
 @import "tailwindcss";
-@import "@nuxt/ui";