US-013 - mTLS encryption for all inter-service communication

[Teboho66]

As a System Administrator, I want all inter-service communication encrypted with mTLS so that security compliance is maintained and no unencrypted traffic flows inside the cluster.

Acceptance Criteria:

• Network traffic scan detects zero unencrypted inter-service connections
• TLS version audit confirms no TLS 1.2 or below connections accepted
• A service without a valid certificate cannot communicate with any other service
• mTLS enforced via service mesh (Istio or Linkerd)

Traceability: NFR-S1
Story Points: 5
Priority: Medium | MoSCoW: Could-have