As a platform operator, I want documentation for the new environment variable configuration option, so that I can understand how to use it.

Context:
Document the new environment variable configuration option for users and operators.

Tasks:

• Update operator deployment documentation to include IMAGE_SHARED_INGRESS_HAPROXY
• Add to the list of supported image override environment variables
• Document use case (shared ingress with HAProxy 2.9+ for PROXY protocol v2 TLV)
• Add troubleshooting guidance

Acceptance Criteria:

• Environment variable documented in operator configuration guide
• Example deployment manifest shows how to set the variable
• Use case clearly explained
• Documentation merged and published