Add SvelteKit adapter API for auth lib

[SOG-web]

Description

Create a comprehensive SvelteKit adapter API for the auth library.

Tasks

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

Acceptance Criteria

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