feat: production-hardened Admin Command Center with RBAC and Emergency Lockdown (#29)

[Ishant5436]

Implementation of a production-hardened administrative dashboard with Role-Based Access Control (RBAC).

Technical details:

• Authorization Gating: Developed a server-side adminRoleGuard middleware that verifies session tokens against the repository's identity provider.
• Emergency Orchestration: Integrated a system-wide lockdown mechanism to freeze registrations and job postings during critical incidents.
• Persistence and Auditing: Automated the capture of all administrative actions into an append-only audit trail for compliance.
• Verification: Verified via the Node.js test suite in apps/api/src/tests/admin.test.js.

Settlement Information:

• Solana: 2WktXRjaQ4GKhj6FJhUSndTBLVjxrk43TQwyywehneDA