Remove shared Tailwind config from backend

Remove the shared Tailwind configuration import and content array
integration from the backend's Tailwind config.

apps/backend/tailwind.config.mjs

@@ -1,16 +1,13 @@
 import tailwindcssAnimate from 'tailwindcss-animate'
 import typography from '@tailwindcss/typography'
-import sharedConfig from '@enchun/shared/tailwind-config-v3'
 
 /** @type {import('tailwindcss').Config} */
 const config = {
-  ...sharedConfig,
   content: [
     './pages/**/*.{ts,tsx}',
     './components/**/*.{ts,tsx}',
     './app/**/*.{ts,tsx}',
     './src/**/*.{ts,tsx}',
-    ...sharedConfig.content,
   ],
   darkMode: ['selector', '[data-theme="dark"]'],
   plugins: [tailwindcssAnimate, typography],