// Package csrf provides Cross-Site Request Forgery (CSRF) protection
// with session-based token storage and form helpers.
//
// # Basic Usage
//
//	// Generate token and store in session
//	token := csrf.GenerateToken(ctx, authManager)
//
//	// In templates - generate hidden input field
//	hiddenField := csrf.HiddenField(ctx, authManager)
//
//	// Verify form submission
//	if !csrf.ValidateToken(ctx, authManager, formToken) {
//		// Handle CSRF validation failure
//	}
//
// # Middleware Integration
//
//	// Add CSRF middleware to protected routes
//	r.Use(middleware.CSRF(authManager))
//
// # Security Features
//
// - Cryptographically secure token generation
// - Session-based token storage and validation
// - Automatic token rotation on successful validation
// - Protection against timing attacks with constant-time comparison
// - Integration with existing authentication system
package csrf