v0.43.0

chore: bump version to 0.43.0 (#274)

* chore: bump version to 0.43.0

New features in this release:
- Cloud Run GPU deployment support (deploy_cloudrun.py, Dockerfile.cloudrun)
- Ensemble preset support in API client (-p/--preset flag in CLI)
- Preset parameter in separate_audio() and separate_audio_and_wait()
- Stem marker stripping for chained separations

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Trigger CI: runners restarted, idle check paused

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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>