feat: minimal prod compose with watchtower auto-updates

backend/Dockerfile

@@ -0,0 +1,21 @@
+# Production image for the FastAPI backend.
+FROM python:3.12-slim
+
+ENV PYTHONUNBUFFERED=1 \
+    PIP_NO_CACHE_DIR=1
+
+COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv
+
+WORKDIR /srv/backend
+COPY pyproject.toml alembic.ini ./
+COPY app ./app
+COPY migrations ./migrations
+COPY scripts ./scripts
+# No lockfile is committed; dependencies resolve at build time.
+RUN uv sync --no-dev
+
+ENV FLOWS_WATCH_ENABLED=true
+EXPOSE 8000
+
+# Migrate on start, then serve (watcher reconciles backend/flows automatically).
+CMD ["sh", "-c", ".venv/bin/alembic upgrade head && exec .venv/bin/uvicorn app.main:app --host 0.0.0.0 --port 8000"]