Add Nuxt adapter API for auth lib #50

Description

Create a comprehensive Nuxt adapter API for the auth library.

Tasks

• Create Nuxt specific middleware
• Implement Nuxt API route handlers for auth endpoints
• Create Nuxt specific session management
• Implement Nuxt specific guards for protected routes
• Add configuration options for Nuxt integration
• Create examples for common Nuxt use cases
• Document Nuxt adapter usage

Acceptance Criteria

• Nuxt adapter works seamlessly with the auth library
• API is intuitive and follows Nuxt/Vue conventions
• Examples cover common use cases
• Documentation is comprehensive