Switch base image to debian and install mise; add py-init helper

Replace FROM python:latest with FROM debian:latest and install curl,
ca-certificates, bash and git. Install mise and add it to PATH, enable
activation in /etc/profile.d/mise.sh and root's .bashrc.

Add /etc/profile.d/py-init.sh which provides a py-init() helper to
initialize mise-managed Python environments (sets mise.toml, venv path
and auto-create). Export the function and ensure non-interactive shells
source it via BASH_ENV.

Set global mise Python to 3.13 and set WORKDIR to /workspace.
CMD remains bash.

Author: koderzi

.devcontainer/docker/Dockerfile

@@ -1 +1,54 @@
-From python:latest
+FROM debian:latest
+
+RUN apt-get update \
+	&& apt-get install -y --no-install-recommends \
+		curl \
+		ca-certificates \
+		bash \
+		git \
+	&& rm -rf /var/lib/apt/lists/* \
+	&& curl -fsSL https://mise.run | sh \
+	&& ~/.local/bin/mise --version || true
+
+ENV PATH="/root/.local/bin:${PATH}"
+
+RUN echo 'eval "$(/root/.local/bin/mise activate bash)"' > /etc/profile.d/mise.sh \
+	&& chmod +x /etc/profile.d/mise.sh || true \
+	&& echo 'eval "$(/root/.local/bin/mise activate bash)"' >> /root/.bashrc
+
+# Provide a convenient py-init() helper for initializing a mise Python
+# environment. Place it in /etc/profile.d so login shells get it, export
+# the function so child bash processes see it, and set BASH_ENV so
+# non-interactive bash shells source it too. Also source it from
+# /root/.bashrc to ensure interactive non-login shells get it.
+RUN cat > /etc/profile.d/py-init.sh <<'PYINIT'
+py-init() {
+  if [ -z "$1" ]; then
+    echo "Error: Please provide a Python version."
+    echo "Example: py-init 3.11"
+    return 1
+  fi
+  
+  echo "Initializing mise Python environment for version $1..."
+  
+  touch ./mise.toml
+  mise use python@$1
+  mise config set env._.python.venv.path .venv
+  mise config set env._.python.venv.create true
+  
+  echo "Setup complete."
+}
+export -f py-init
+PYINIT
+
+RUN chmod 0755 /etc/profile.d/py-init.sh \
+		&& echo 'source /etc/profile.d/py-init.sh' >> /root/.bashrc || true
+
+# Ensure non-interactive bash shells source the py-init helper
+ENV BASH_ENV=/etc/profile.d/py-init.sh
+
+RUN /root/.local/bin/mise use --global python@3.13
+
+WORKDIR /workspace
+
+CMD ["bash"]