feat(vision): il worker che espone il runner, versione stampata al build

Container FastAPI separato (Dockerfile.vision, python:3.13-slim) che
espone run_graph/engine_version del Task 2 via POST /run e GET /health,
cosi' l'immagine del server principale non importa mai VisionSuite.

engine_version() ora legge VISION_ENGINE_VERSION se impostata, altrimenti
ricade su git rev-parse nel checkout di sviluppo, e non inventa mai un
valore: senza nessuna delle due solleva un errore esplicito. Nel container
il fallback a git non puo' funzionare (.git del submodule punta fuori dal
build context), quindi Dockerfile.vision prende il commit come build arg
e lo fissa in ambiente; i compose file lo passano da VISION_ENGINE_VERSION.

Nessuna porta pubblicata e nessuna label Traefik sul servizio vision: e'
raggiungibile solo dal server, su tmflow-net.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014BBnuACZSCJqXrMYC3LUMU

Dockerfile.vision

@@ -0,0 +1,33 @@
+FROM python:3.13-slim
+
+# opencv-python (pulled in transitively by vs-core/vs-task/vs-measure/vs-pm2d)
+# needs libGL and glib at runtime even though it is never imported by name here.
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        libgl1 libglib2.0-0 \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv
+
+WORKDIR /app
+COPY pyproject.toml uv.lock ./
+COPY vendor/ ./vendor/
+RUN uv sync --extra vision --frozen --no-dev
+
+COPY src/vision/ ./src/vision/
+COPY src/vision_worker/ ./src/vision_worker/
+
+# Ruling R8: the version is stamped at build time, not discovered at runtime.
+# COPY vendor/ above does not bring vendor/visionsuite/.git along - it is a
+# gitlink file pointing at ../../.git/modules/vendor/visionsuite, which lives
+# outside the build context - so `git rev-parse HEAD` cannot work in here.
+# Pass the submodule's commit in from the host, which does have git:
+#   VISION_ENGINE_VERSION=$(git -C vendor/visionsuite rev-parse HEAD) \
+#     docker compose build vision
+ARG VISION_ENGINE_VERSION
+ENV VISION_ENGINE_VERSION=${VISION_ENGINE_VERSION}
+
+EXPOSE 8100
+
+# Two workers, not four: each holds the vision stack in memory.
+CMD ["uv", "run", "uvicorn", "src.vision_worker.main:app", \
+     "--host", "0.0.0.0", "--port", "8100", "--workers", "2"]