ace-step + stable-audio-open: deploy music + SFX generation to irv-ml1

Two new audio-generation stacks alongside the TTS slate:

ace-step :8210 — Apache 2.0 music generation foundation model
(hybrid diffusion + LLM). Lyric-aware multi-minute songs. ~10-12 GB
VRAM during inference, A6000-pinned. Custom Dockerfile patches
upstream's torch/cu126 resolution bug (--extra-index-url cu126 was
falling back to pypi-default cu13 wheels, mismatching torchvision).

stable-audio-open :8211 — Stability AI 1.21B latent-diffusion SFX +
ambience. Up to 47s clips at 44.1 kHz. ~6 GB VRAM in fp16,
A6000-pinned. Custom FastAPI shim around diffusers' StableAudioPipeline
(no upstream HTTP server). Dockerfile pins torchsde explicitly —
diffusers doesn't pull it as a hard dep but
CosineDPMSolverMultistepScheduler needs it.

stacks/stable-audio-open/Dockerfile

@@ -0,0 +1,43 @@
+# Stable Audio Open 1.0 inference image.
+# pytorch/pytorch base ships torch + cuda + cudnn already linked, so
+# we only layer the diffusers stack + a libsndfile for soundfile + the
+# fastapi shim. Smaller and faster to build than starting from
+# nvidia/cuda and pip-installing torch ourselves.
+FROM pytorch/pytorch:2.5.1-cuda12.4-cudnn9-runtime AS base
+
+ENV PYTHONUNBUFFERED=1 \
+    PYTHONDONTWRITEBYTECODE=1 \
+    PIP_NO_CACHE_DIR=1 \
+    PIP_DISABLE_PIP_VERSION_CHECK=1 \
+    HF_HOME=/app/hf_cache
+
+# libsndfile1 is the C lib soundfile binds to. Without it the pip
+# install of soundfile succeeds but `import soundfile` fails at
+# runtime with OSError: cannot find libsndfile.
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        libsndfile1 \
+    && rm -rf /var/lib/apt/lists/*
+
+# protobuf + sentencepiece are pulled in by the T5 text encoder
+# (Stable Audio Open uses google/t5-base-cb under the hood).
+# accelerate gates the .to(device) fast path for diffusers.
+# torchsde is required by CosineDPMSolverMultistepScheduler — diffusers
+# doesn't pull it as a hard dep; without it, pipeline init fails with
+# "CosineDPMSolverMultistepScheduler requires the torchsde library".
+RUN pip install \
+        "diffusers>=0.27.0" \
+        "transformers>=4.40.0" \
+        accelerate \
+        protobuf \
+        sentencepiece \
+        soundfile \
+        torchsde \
+        fastapi \
+        "uvicorn[standard]" \
+        pydantic
+
+WORKDIR /app
+COPY server.py /app/server.py
+
+EXPOSE 8000
+CMD ["uvicorn", "server:app", "--host", "0.0.0.0", "--port", "8000"]