Fix Space startup: use sh instead of missing bash

Dockerfile

@@ -15,7 +15,7 @@ FROM python:3.12-slim
 COPY --from=ghcr.io/astral-sh/uv:latest /uv /uvx /bin/
 RUN useradd -m -u 1000 user
 WORKDIR /app
-RUN apt-get update && apt-get install -y --no-install-recommends git curl && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y --no-install-recommends git curl ca-certificates && rm -rf /var/lib/apt/lists/*
 
 RUN git clone --depth 1 https://huggingface.co/spaces/smolagents/ml-intern /tmp/source && \
     cp /tmp/source/pyproject.toml /tmp/source/uv.lock ./ && \
@@ -43,4 +43,5 @@ ENV HOME=/home/user \
 
 EXPOSE 7860
 WORKDIR /app/backend
-CMD ["bash", "start.sh"]
+# python:slim does not include bash by default; start.sh is POSIX-compatible.
+CMD ["sh", "start.sh"]