StemRoller: desktop stem separator, Android stems player, and server daemons

- stemroller/: PySide6/QML desktop app and player for separating music into stems
- android/: Plex music player that plays per-stem mixes, with Android Auto support,
  a graphic + parametric (Equalizer APO-style) EQ, and offline downloads
- server/: stemserve (serves stems to the app) and stemd (separates the library on
  the server's GPU, with "Stem Now" priority requests)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/stemd.Dockerfile

@@ -0,0 +1,24 @@
+# stemd: separates new music into stems on the server's NVIDIA GPU (see stemd.py).
+# Build from the repo root, since it needs the stemroller package:
+#   docker build -f server/stemd.Dockerfile -t stemd .
+FROM python:3.12-slim
+RUN apt-get update && apt-get install -y --no-install-recommends ffmpeg && rm -rf /var/lib/apt/lists/*
+# cu126 runs on NVIDIA driver 525 and up. TORCH_INDEX=cpu builds a small GPU-less image for testing.
+ARG TORCH_INDEX=cu126
+RUN pip install --no-cache-dir torch==2.14.1 torchvision==0.29.1 --index-url https://download.pytorch.org/whl/${TORCH_INDEX}
+COPY server/stemd-requirements.txt /tmp/
+# Everything is pinned, so --no-deps keeps pip from swapping torch for a non-CUDA build.
+# gcc is only for diffq, which has no wheel.
+RUN apt-get update && apt-get install -y --no-install-recommends gcc libc6-dev \
+ && pip install --no-cache-dir --no-deps -r /tmp/stemd-requirements.txt && pip check \
+ && apt-get purge -y gcc libc6-dev && apt-get autoremove -y && rm -rf /var/lib/apt/lists/*
+COPY stemroller/__init__.py stemroller/catalog.py stemroller/library_core.py /app/stemroller/
+COPY stemroller/worker/__init__.py stemroller/worker/__main__.py stemroller/worker/audio_io.py \
+     stemroller/worker/backends.py /app/stemroller/worker/
+COPY server/stemd.py /app/server/
+ENV MUSIC_DIR=/music STEMS_DIR=/stems STATE_DIR=/state MODELS_DIR=/models \
+    TORCH_HOME=/models/torch HF_HOME=/models/hf NUMBA_CACHE_DIR=/tmp/numba HOME=/tmp \
+    PYTHONUNBUFFERED=1 PYTHONDONTWRITEBYTECODE=1 PYTHONWARNINGS=ignore::FutureWarning
+# Unraid shares belong to nobody:users.
+USER 99:100
+CMD ["python", "/app/server/stemd.py"]