Add role-based access control for admin endpoints

[meshackyaro]

Description

Admin endpoints (verifyUser, migrations) accessible by any authenticated user. No role enforcement.

Component

Backend

Difficulty

🔴 Hard

Tasks

• Design role model (admin, juror-manager, user)
• Add role claim to JWT payload
• Implement RolesGuard
• Apply guards to privileged endpoints
• Document role requirements

Acceptance Criteria

• Admin endpoints require admin role
• Roles enforced consistently
• Role model documented

Estimated Time

3-5 days