[refactor]: relocate backend entrypoint outside bind mount

Moved entrypoint.sh copy target from /app/entrypoint.sh to
/entrypoint.sh in the dev Dockerfile. The dev compose bind mount
./backend:/app overlays /app entirely; placing the entrypoint above
that boundary ensures the image-baked script is never shadowed by
host directory contents. No startup failure was reproduced — this
is a preventive hardening change.

PROJECTS/advanced/ai-threat-detection/infra/docker/fastapi.dev

@@ -31,11 +31,11 @@ COPY backend/pyproject.toml ./
 RUN uv pip install --system -e ".[dev,ml]"
 
 COPY backend/ .
-COPY infra/docker/entrypoint.sh /app/entrypoint.sh
-RUN chmod +x /app/entrypoint.sh && \
+COPY infra/docker/entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh && \
     mkdir -p /app/data/models
 
 EXPOSE 8000
 
-ENTRYPOINT ["/app/entrypoint.sh"]
+ENTRYPOINT ["/entrypoint.sh"]
 CMD ["uvicorn", "app.factory:create_app", "--factory", "--host", "0.0.0.0", "--port", "8000", "--reload"]