Migrate Tailwind styles to design-system package (#5794)

## Summary

Consolidates Tailwind configuration and styles into a shared
`@comfyorg/design-system` package for reuse across monorepo apps.

The goal was not to make changes to how the design system works; merely
to separate it cleanly. I _would_ strongly recommend some drastic
sweeping changes, however I believe that should be done after the
migration.

## Changes

- **What**: Migrates CSS files, Tailwind config, and custom icons to
design-system package
- **Dependencies**: Moves `@iconify-json/lucide` and `@iconify/tailwind`
to design-system package

vitest.config.ts

@@ -9,7 +9,7 @@ export default defineConfig({
     Icons({
       compiler: 'vue3',
       customCollections: {
-        comfy: FileSystemIconLoader('src/assets/icons/custom')
+        comfy: FileSystemIconLoader('packages/design-system/src/icons')
       }
     })
   ],