WA-NEW-012: Run CI on Ruby 3.2

[kitcommerce]

Summary

Update GitHub Actions CI workflow to run on Ruby 3.2.

This unblocks CI because workarea-core requires Ruby >= 2.7.0.

Closes #636

Client impact

None. CI-only change.

Verify

• CI bundle install step succeeds (no Ruby version solver failure)
• CI jobs progress into test execution

[kitcommerce]

Update: CI failures on this PR were not Ruby solver-related anymore; they were due to:

1. workarea:services requiring docker-compose binary (runner only has docker compose / plugin). Added a step to install docker-compose via apt in all test jobs.
2. workarea-commerce/ci/* docker-based actions for bundler-audit/rubocop are pinned to ruby:2.6 and cannot bundle workarea-core (>=2.7). Replaced those steps with running bundler-audit + rubocop directly under ruby/setup-ruby (3.2) in static_analysis.

Next CI run should get past service startup + static analysis tooling.

[kitcommerce]

Dispatcher Build Gate Summary (local)

• rubocop (diff-only): N/A (no Ruby files changed)
• brakeman: skipped (per repo build gate config; disabled)
• tests: N/A (no engine code changed)

Labeled gate:build-passed.