Fix CI & update versions

Changes:

• use Docker image from Harbor registry instead of internal GitLab Dependency Proxy in the Kaniko build step
• use debian:stable-slim (currently Bookworm) image instead of debian:bullseye-slim
• remove reference to SubApp-related Docker image target (probably copy&paste bug)
• update Rosetta SDK version to 8.2 (prev. 7.3)

Changed files:

• /gitlab-ci/Dockerfile
• /.gitlab-ci.yml

gitlab-ci/Dockerfile

-FROM git.slub-dresden.de/debian-packaging/dependency_proxy/containers/debian:bullseye-slim
+FROM sdvharbor.slub-dresden.de/replication/debian:stable-slim
 
 ARG GITDIR
 ENV DEBIAN_FRONTEND=noninteractive
@@ -9,7 +9,7 @@ ENV EXLIBRIS_PATH=/exlibris
 RUN apt-get update; \
     apt-get install -y --no-install-recommends gnupg wget; \
     wget -O - http://sdvdebianrepo.slub-dresden.de/deb-repository/pub.gpg.key | apt-key add - ; \
-    echo "deb http://sdvdebianrepo.slub-dresden.de/deb-repository bullseye main" > /etc/apt/sources.list.d/slub.list;
+    echo "deb http://sdvdebianrepo.slub-dresden.de/deb-repository bookworm main" > /etc/apt/sources.list.d/slub.list;
 
 RUN apt-get update; \
     apt-get -y upgrade; \