v0.44.0

feat: add GCS URI support to /separate endpoint (#277)

Allow callers to pass a gcs_uri (gs://bucket/path) instead of uploading
the audio file as a multipart POST body. This avoids Cloud Run's 32MB
request body limit for large FLAC files.

- Server: new gcs_uri parameter on /separate, downloads from GCS directly
- Client: separate_audio() and separate_audio_and_wait() accept gcs_uri
- Backward compatible: file upload still works when gcs_uri is not set
- Version bump to 0.44.0

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