feat: auto-detect public IP for geth P2P peer discovery

[Kewe63]

Previously, HOST_IP was hardcoded to empty string and users had to manually edit the entrypoint to enable --nat=extip. This change:

• Adds the same get_public_ip() function used by base-consensus-entrypoint and op-node-entrypoint (tries ifconfig.me, api.ipify.org, ipecho.net, v4.ident.me in sequence)
• Auto-detects public IP if HOST_IP is not manually set
• Falls back gracefully with a warning if detection fails
• Respects manual HOST_IP override when set via environment

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.