docs: document Reth port and log level variables in env files

[erhnysr]

Summary

Adds commented-out documentation for Reth-specific port and log level variables that are supported by reth-entrypoint but were completely absent from the env files.

Problem

Operators who want to customize Reth ports (e.g. running multiple nodes, resolving port conflicts) or change log verbosity had no way to discover these variables without reading the entrypoint source code directly.

Changes

Added documented, commented-out entries to both .env.mainnet and .env.sepolia:

Variable	Default	Description
RPC_PORT	8545	HTTP JSON-RPC port
WS_PORT	8546	WebSocket JSON-RPC port
AUTHRPC_PORT	8551	Engine API (authenticated RPC) port
METRICS_PORT	6060	Prometheus metrics port
DISCOVERY_PORT	30303	P2P discovery port
V5_DISCOVERY_PORT	9200	discv5 discovery port
P2P_PORT	30303	P2P TCP port
LOG_LEVEL	info	Reth log verbosity (error/warn/info/debug/trace)

Verification

All variables verified against reth/reth-entrypoint source.

[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 0 Sum 1

[erhnysr]

Rebased on latest main (post #1090)

The PR has been rebased onto the current main branch. After #1090 unified the client entrypoints, execution-entrypoint already defines all of these variables — but they remain undocumented in the .env files, so operators still can't discover them without reading the entrypoint source.

Changes (.env.mainnet and .env.sepolia):

Added two new commented-out sections before the existing PRUNING block:

# PORT CONFIGURATION (OPTIONAL - UNCOMMENT TO OVERRIDE DEFAULTS)
# RPC_PORT=8545          # HTTP JSON-RPC port
# WS_PORT=8546           # WebSocket JSON-RPC port
# AUTHRPC_PORT=8551      # Engine API (authenticated RPC) port
# METRICS_PORT=6060      # Prometheus metrics port
# DISCOVERY_PORT=30303   # P2P discovery port
# V5_DISCOVERY_PORT=9200 # discv5 discovery port
# P2P_PORT=30303         # P2P TCP port

# LOG LEVEL (OPTIONAL - UNCOMMENT TO OVERRIDE DEFAULT)
# Supported values: error, warn, info, debug, trace (default: info)
# LOG_LEVEL=info

All variables verified against the current execution-entrypoint. No behaviour change — purely additive documentation. Happy to address any feedback.