Feature/new guard

[NayanthaRC]

This pull request introduces role-based dashboards and authentication guards for "Administrator", "Model Trainer", and "Super Admin" roles in the Global Classifier application. It adds backend endpoints and frontend pages for each dashboard, implements role-based routing and access control, and defines the necessary role constants and environment variables.

Key changes:

Backend: Role-based dashboards and guards

• Added new endpoints and authentication guards for /admin/dashboard, /model-trainer/dashboard, and /super-admin/dashboard, each with its own guard logic and authority check templates. These endpoints return role-specific dashboard data. [1] [2] [3] [4] [5] [6] [7] [8]
• Introduced a public test endpoint for checking current user info via JWT.
• Updated .env.example to include a mapping for the ROLE_SUPER_ADMIN.

Frontend: Dashboard pages and routing

• Added new React pages and SCSS styles for AdminDashboard, ModelTrainerDashboard, and SuperAdminDashboard, each displaying user info and permissions relevant to the role. [1] [2] [3]
• Updated App.tsx to import these dashboards, define role constants, and add role-based routes that render the appropriate dashboard or an unauthorized message based on user authorities. [1] [2] [3]
• Added an export for the new AdminDashboard component.

These changes collectively provide a foundation for secure, role-specific access and user experience in the application.