image: switch to Debian 13 "Trixie"

NB: Angie repository for Debian 13 is coming soon.

Dockerfile.base

@@ -1,5 +1,5 @@
-# FROM docker.io/debian:bookworm-slim as base-upstream
-ARG PYTHONTAG=3.12.11-slim-bookworm
+# FROM docker.io/debian:trixie-slim as base-upstream
+ARG PYTHONTAG=3.12.11-slim-trixie
 FROM docker.io/python:${PYTHONTAG} AS base-upstream
 
 FROM base-upstream AS base-intermediate
@@ -19,7 +19,6 @@ ENV PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin \
     PYTHONUNBUFFERED=1 \
     PYTHONDONTWRITEBYTECODE=1
 
-COPY /apt/prefs.backports  /etc/apt/preferences.d/backports
 COPY /apt/sources.debian   /etc/apt/sources.list.d/debian.sources
 
 ## prevent services from auto-starting, part 1
@@ -60,6 +59,7 @@ RUN apt-env.sh apt-get update ; \
       openssl \
       procps \
       psmisc \
+      systemd-standalone-sysusers \
       tzdata \
       zstd \
     ; \