build(typography): add Tailwind Typography plugin for markdown preview styles

- Install @tailwindcss/typography package
- Configure Typography plugin in tailwind.config.js
- Adds prose and dark:prose-invert classes for styled markdown output

frontend/tailwind.config.js

@@ -6,5 +6,7 @@ export default {
   theme: {
     extend: {},
   },
-  plugins: [],
+  plugins: [
+    require('@tailwindcss/typography'),
+  ],
 }