Docker: Debian 13 RC with PHP 8.4 (#7772)

Help final testing of Debian 13 Trixie before the release (9 August)
https://lists.debian.org/debian-devel-announce/2025/07/msg00003.html
PHP 8.4.10, Apache 2.4.64
I will make another PR after the release to update to `debian:13-slim` when it gets available.

Docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM debian:12-slim
+FROM debian:trixie-slim
 
 ENV TZ=UTC
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]