Full-Stack Developer for Secure Access Control & User Roles

I need an experienced full-stack developer to add secure role-based access control to my existing, fully functional website. The site has about 10 sections, including Shop, Podcast, Bookshop, News/Blog, Catering, and others. Each staff member should only have access to the section(s) they are hired to work on, while Owner, Admin, Privacy, financial, and other restricted areas remain protected. Access must be secured at the backend level so restrictions cannot be bypassed through direct URLs or other methods. Unauthorized access should be blocked. The website already has a login/sign-in system. I want to add professional moving visuals and animations to the existing sign-in/welcome areas to create a smooth and professional transition after login. The website is already working properly. No rebuild is necessary. Please apply only if you have experience with backend security, authentication, role-based access control, and full-stack development. Please provide examples of similar work.