Normalize incoming ID parameters to integers and replace concatenated/raw SQL with CodeIgniter query builder. Controllers (Contesting.php, Themes.php) now cast $id to (int) instead of using xss_clean; models (Contesting_model.php, Themes_model.php) cast $id and use $this->db->where()/get()/select() to build queries. This improves type safety and reduces risk of injection while using more idiomatic CI DB APIs.