Role UX enforcement: block non-admin access to admin pages pre-API call

[ApexYash11]

Summary

Enforce admin role checks in UI routing before privileged pages initiate API calls.

Why

Current improvement plan highlights reliability/security gaps when role checks happen late.

Scope

• Add pre-render/pre-fetch admin role guards for admin routes.
• Hide or redirect non-admin users before admin API calls execute.
• Keep server-side auth checks as authoritative (UI check is additive).
• Add test coverage for admin vs non-admin route behavior.

Acceptance Criteria

• Non-admin users cannot access admin UX paths.
• Admin API calls are not triggered for unauthorized users from UI.
• Redirect/denied states are consistent and user-friendly.

Source

• docs/SITE_FLOW_AND_IMPROVEMENTS.md (Improvement Plan Fix React Server Components CVE vulnerabilities #5, Success Criteria)