fix: add HOST_IP support and strict LOG_LEVEL validation to reth entrypoint

[Kewe63]

Summary

Implements HOST_IP advertisement for NAT traversal and adds strict LOG_LEVEL validation to the Reth entrypoint.

Problem

• Reth nodes behind NAT struggled with peer discovery because the external IP was not advertised.
• The temporary reth node used for historical proofs initialization did not receive the NAT configuration.
• Unknown LOG_LEVEL values were silently falling back to defaults without notifying the operator.
• Unvalidated HOST_IP inputs could lead to shell expansion issues.

Solution

• Implemented a dedicated NAT_ARG that is passed to both the temporary initialization node and the final execution process.
• Added IPv4 regex validation for HOST_IP for security and robustness.
• Added a strict case statement for LOG_LEVEL validation that exits with an error on unknown values.

Verification

• Verified NAT flag propagation to both process instances.
• Tested LOG_LEVEL validation with invalid inputs.

Impact

Significantly improves P2P connectivity for operators behind NAT and enhances operational reliability through strict input validation.

[cb-heimdall]

🟡 Heimdall Review Status

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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