Create columns to track settlement gas info

[jmg-duarte]

Description

#4540 requires that the migration is done first to avoid issues when upping it in K8s

This PR adds the settlement gas info columns to the settlement table.

Changes

• Adds gas_used column to settlement table
• Adds effective_gas_price to settlement table

[github-actions]

Reminder: Please update the DB Readme and comment whether migrations are reversible (include rollback scripts if applicable).

• If creating new tables, update the tables list.
• When adding a new index, consider using CREATE INDEX CONCURRENTLY for tables involved in the critical execution path.
• For breaking changes, remember that during rollout k8s starts the new autopilot, runs the Flyway migration, and only then shuts down the old pod. That overlap means the previous version can still be processing requests on the migrated schema, so make it compatible first and ship the breaking DB change in the following release.

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Caused by:

• database/sql/V116__settlement_gas_cost.sql

[claude]

Claude finished @jmg-duarte's task in 1m 7s —— View job

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PR Review: Settlement gas info columns

• Read PR changes
• Review migration correctness & conventions
• Check DB readme / tables list requirements
• Post findings

The migration looks solid — additive nullable columns with numeric(78,0), which matches the u256 convention used throughout the schema (and the existing gas_used numeric(78,0) in V048__create_settlement_rewards.sql). Since the columns are nullable and unreferenced by the old code, it's safe for the k8s rollout overlap, which aligns with the "migration first" strategy described in the PR.

Two small points posted inline:

• Update the DB README — the settlements table docs don't yet list gas_used / effective_gas_price (per the bot reminder).
• Stray ) in the comment after "observer".

Neither is blocking.

[claude]

The bot reminder asks to update the DB README when adding columns. The settlements table docs still don't list gas_used / effective_gas_price — worth adding the two rows so the schema doc stays in sync.

Type/naming look good: numeric(78,0) matches the u256 convention used elsewhere (and the existing gas_used numeric(78,0) in V048__create_settlement_rewards.sql), and nullable additive columns are backward-compatible with the k8s rollout overlap.

[MartinquaXD]

Probably makes sense to keep the columns separately for higher flexibility but do we currently plan on using those values separately?