fix(remote): unblock audio-separator-remote for typical files (#288)

* fix(remote): unblock audio-separator-remote for typical files

Two independent issues prevented `audio-separator-remote` from working
end-to-end against the GCP Cloud Run deployment:

1. **CLI hits Cloud Run's 32 MiB request body limit on real audio files.**
   The underlying AudioSeparatorAPIClient already supports a `gcs_uri`
   mode where the server fetches from GCS (used by karaoke-gen), but the
   CLI only exposed the multipart upload path. Now the CLI detects files
   >30 MiB and auto-uploads to GCS, passes `gcs_uri` to the API, and
   cleans up the GCS object in a `finally` block (the bucket's 1-day
   lifecycle is the safety net). Bucket configurable via `--gcs-bucket`
   or `AUDIO_SEPARATOR_GCS_INPUT_BUCKET`; defaults to the existing
   `nomadkaraoke-audio-separator-outputs` (separator SA already has
   objectAdmin, no infra change needed). `google-cloud-storage` is
   lazy-imported with a clear install hint if missing.

2. **Cloud Run server silently runs in CPU mode, not GPU.** The image
   relied on `pip install ".[gpu]"` for GPU support, which only swaps in
   `onnxruntime-gpu` — the `torch>=2.3` constraint pulls PyPI's default
   CPU-only PyTorch wheel. Result: `torch.cuda.is_available()` returns
   False, Separator falls back to CPU, jobs run ~10x slower (50 min
   instead of 5 min for the vocal_balanced preset). karaoke-gen's
   audio-separation-job image already documents this gotcha in
   `Dockerfile.gpu-base:100-106`; mirroring that pattern here:
   install `torch==2.6.0+cu126` from the cu126 index first so
   audio-separator[gpu] sees torch as already satisfied.

Tests: 7 new unit tests covering GCS upload helpers (blob path format,
URI parsing, error handling), bucket resolution priority (--flag > env >
default), and the integration into handle_separate_command (large/small
file, cleanup on failure, upload failure).

Bumps version to 0.44.2.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* test: pass gcs_bucket to handle_separate_command in integration test

Missed this call site when updating the function signature. Unit tests
in tests/unit/test_remote_cli.py were updated, but integration test
test_cli_separate_command_integration still passed only 3 args.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>