Update frontend and backend configurations for new port settings and authentication flow

Commit notes

- Changed frontend port from 3000 to 4000 in Vite configuration and related files. - Updated backend environment variables for FRONTEND_URL and ALLOWED_ORIGINS to reflect the new port. - Refactored authentication components to streamline the user experience, removing the login modal and integrating Google OAuth directly. - Adjusted various routes and components to ensure consistent navigation and user flow without the need for a dedicated login page. - Enhanced error handling and user feedback during authentication processes.