CI: add debian-13 images

ci/images/full/debian-13/Dockerfile

+FROM registry.nic.cz/packaging/apkg/systemd/debian-13
+ENV DEBIAN_FRONTEND=noninteractive
+
+WORKDIR /root
+CMD ["/bin/bash"]
+
+# upgrade system to latest
+RUN apt-get update -qqq
+RUN apt-get upgrade -y -qqq
+
+# packaging deps
+RUN apt-get install -y -qqq \
+    apt-utils \
+    build-essential \
+    curl \
+    debhelper \
+    dh-python \
+    dpkg-dev \
+    git \
+    python3-all \
+    python3-pip \
+    python3-setuptools \
+    pipx
+# apkg deps
+RUN apt-get install -y -qqq \
+    python3-bs4 \
+    python3-blessed \
+    python3-build \
+    python3-click \
+    python3-distro \
+    python3-jinja2 \
+    python3-packaging \
+    python3-requests \
+    python3-toml
+# install stable apkg from PyPI
+RUN python3 -m pip install --break-system-packages apkg
+RUN apkg --version