Kavith Mathushal contributed to the eSupportTechnology/Booking-website project by establishing the initial routing scaffolding for user authentication, creating foundational PHP files to support future authentication features. He focused on backend development and database migration, addressing a migration error in the files table by making the property_id field nullable and preventing unintended foreign-key drops, which improved deployment stability. His work involved iterative refactoring to enhance code maintainability and support smoother feature rollouts. By prioritizing secure authentication groundwork and stabilizing database changes, Kavith enabled more reliable releases and set the stage for further development within the PHP-based backend architecture.