[Connector] Improve offline match endpoint authentication

[Flegma]

Summary

The offline match management endpoint authentication mechanism needs strengthening to use proper secrets.

Tasks

• Replace current authentication credentials with a dedicated secret
• Ensure credentials are not derivable from public information

Impact

Could allow unauthorized access to match management endpoints.

Details

Full details in internal audit document. Finding IDs: HIGH-CONN-05

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Related Issues (Security Hardening Pattern)

• [Infrastructure] Tighten RBAC cluster roles & DaemonSet security context #412 — [Infrastructure] Tighten RBAC & DaemonSet security
• [Infrastructure] Add network policies & scope Vault permissions per service #413 — [Infrastructure] Network policies & Vault scoping
• [Connector] Improve offline match endpoint authentication #409 — [Connector] Improve offline match authentication
• [API] Strengthen request authentication and proxy trust validation #372 — [API] Strengthen request authentication