feat(pipewire): Add alsa integration

Any programs running through alsa only (such as spotify_player on
voidlinux) should now also work correctly through the pipewire stack.

roles/display_manager/templates/greetd-config.toml.j2

@@ -5,9 +5,14 @@ vt = 7
 
 # The default session, also known as the greeter.
 [default_session]
-command = "tuigreet --cmd zsh"
+command = "tuigreet --cmd {{ dm_command }}"
+command = "tuigreet --power-reboot 'sudo reboot' --power-shutdown 'sudo poweroff' --cmd {{ dm_command }}"
 user = "{{ greeter_user }}"
 
+[initial_session]
+command = "{{ dm_command }}"
+user = "{{ user_name | default('root') }}"
+
 # `agreety` is the bundled agetty/login-lookalike. You can replace `/bin/sh`
 # with whatever you want started, such as `sway`.
 # command = "agreety --cmd /bin/sh"