Play Framework

Add Nuxt 3 frontend option to play new (Phase 4)

Add --frontend=nuxt flag to play new that creates a decoupled
Nuxt 3 + Tailwind CSS frontend alongside the Play application:

  play new myapp --name=MyApp --frontend=nuxt

This creates:
- frontend/ directory with Nuxt 3, Tailwind CSS, TypeScript
- Proxy config routing /api/** to Play backend (port 9000)
- Default layout, index page that fetches /api/status
- useApi composable for backend calls
- ApiController.java in the Play app with a status endpoint
- API route added to conf/routes

Architecture: Nuxt runs as a separate dev server (port 3000)
and proxies API calls to Play. For production, use nuxt generate
to create static files or nuxt build for SSR.

Includes 4 new CLI tests verifying frontend scaffolding.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>