CI Fixes
docs-sync: Updated docs/openapi.yaml version 2.2.0 → 2.2.3, added required ## [Unreleased] section to CHANGELOG.md — resolved check:docs-sync CI lint failures.
Electron Linux .deb: Added gem install fpm step to Linux build job in electron-release.yml — electron-builder requires the fpm Ruby gem to package .deb installers, but it's not pre-installed on ubuntu-latest runners.
Docker publish: Previous 502 error writing layer blob was a transient Docker Hub network error. Added DOCKER_BUILDKIT_INLINE_CACHE env for improved caching on multi-arch ARM64 push.