feat(dots-tts): ship OpenAI-compatible dots.tts TTS stack on irv-ml1:8198

Thin FastAPI wrapper over DotsTtsRuntime (soar, optimize=True, RTF ~0.22),
serialized single-consumer; OpenAI /v1/audio/speech (stream + non-stream),
voices from the voices/ corpus derived set. Live + healthy alongside
chatterbox-fast on the 3090; nothing repointed. Dockerfile needs
build-essential (torch.compile/inductor JITs via gcc at runtime) + persisted
inductor cache. Remaining Phase-2: ratatoskr client cutover.

stacks/dots-tts/Dockerfile

@@ -0,0 +1,34 @@
+# dots.tts OpenAI-compatible TTS server (thin FastAPI over DotsTtsRuntime).
+# GPU access is via `runtime: nvidia` at run time (torch ships its own CUDA
+# runtime; no CUDA toolkit / nvcc needed to build — the model uses no custom
+# compiled kernels, confirmed on the irv-ml1 venv).
+FROM python:3.11-slim
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        libsndfile1 ffmpeg git curl ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN pip install --no-cache-dir uv
+
+WORKDIR /app
+
+# Pin torch + deps to dots.tts upstream recommended constraints (the same set the
+# irv-ml1 venv installed against). ADD caches on the URL contents.
+ADD https://raw.githubusercontent.com/rednote-hilab/dots.tts/main/constraints/recommended.txt /tmp/rec.txt
+RUN uv pip install --system -c /tmp/rec.txt \
+        dots.tts soundfile fastapi "uvicorn[standard]"
+
+# C compiler for the RUNTIME (not build): optimize=True drives torch.compile /
+# inductor / triton, which JIT-compile kernels via gcc on model load. Without it
+# the runtime dies with "Failed to find C compiler". Placed after the pip layer
+# so it doesn't invalidate the expensive torch install cache.
+RUN apt-get update && apt-get install -y --no-install-recommends build-essential \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY app.py /app/app.py
+
+# Persist the inductor compile cache on the mounted (rw) HF cache so kernel
+# JIT doesn't re-run on every container restart (~70s warmup otherwise).
+ENV HF_HOME=/hf_cache DOTS_PORT=8198 CC=gcc CXX=g++ TORCHINDUCTOR_CACHE_DIR=/hf_cache/inductor
+EXPOSE 8198
+CMD ["uvicorn", "app:app", "--host", "0.0.0.0", "--port", "8198"]