Describe the feature you'd like
Implement Apple Sign-In authentication for iOS users to provide a seamless login experience and comply with Apple's authentication requirements for apps that offer third-party login options.

Reference

• Apple Developer - Sign in with Apple
• sign_in_with_apple Flutter package
• Apple Human Interface Guidelines - Sign in with Apple

Additional context

• Should integrate with existing BLoC authentication state management
• Required for App Store compliance when other social logins are present
• Need to handle Apple ID credential validation and user data persistence
• Consider fallback UI for non-iOS platforms or unsupported iOS versions
• Should work alongside existing login methods in the scheduling app

Acceptance Criteria:

• Apple Sign-In button appears on login screen
• Successful authentication updates auth BLoC state
• User profile data is properly handled and stored
• Proper error handling for failed authentication attempts