✨ Implement Google OAuth authentication and event claiming functionality

- Added Google OAuth integration with OmniAuth for user authentication. - Created Users table with fields for email, name, Google ID, and avatar URL. - Updated Events table to include a user reference for claimed events. - Implemented SessionsController for handling sign-in, sign-out, and failure actions. - Created EventClaimsController to manage claiming events by users. - Updated views for sign-in, event claiming, and event management. - Enhanced header and footer for user authentication state. - Added routes for authentication and event claiming. - Configured OmniAuth initializer for Google OAuth. - Updated application layout and styles for improved user experience.