Keep the media-pi roles working on trixie

- pi_hifiberry_amp: the boot config lives at /boot/firmware/config.txt.
- pi_sysdweb: install python3-dbus and python3-systemd from apt, which trixie ships at
  the versions sysdweb needs; bookworm gets the headers pip needs to build dbus-python
  1.4 itself.
- pi_squeezeserver: trixie images have no iptables, and so cannot have the port 80
  redirect that absent.yml removes - skip that step there instead of failing.
- pi_modern_shell_env, pi_slint_frontend: read facts through `ansible_facts` rather than
  the deprecated injected `ansible_*` variables.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

roles/pi_modern_shell_env/tasks/main.yml

@@ -34,7 +34,7 @@
     # build: TLS handshake fails with SSL_ERROR_SYSCALL), while Ansible's
     # get_url (Python urllib) succeeds against the same CDN. Download the
     # binary directly instead of shelling out to the install script.
-    url: "https://cdn.ohmyposh.dev/releases/latest/posh-linux-{{ pi_modern_shell_env_ohmyposh_arch_map[ansible_architecture] }}"
+    url: "https://cdn.ohmyposh.dev/releases/latest/posh-linux-{{ pi_modern_shell_env_ohmyposh_arch_map[ansible_facts['architecture']] }}"
     dest: /usr/local/bin/oh-my-posh
     mode: "0755"