fix: add playbook_help role to livekit.yml for retries variables

devture_playbook_help_container_retries_count/delay are defined by
galaxy/playbook_help and required by install.yml image pull tasks.

https://claude.ai/code/session_01SbRgWsRDKpTZ2TTbWDhtEB

livekit.yml

@@ -10,6 +10,8 @@
   become: true
 
   roles:
+    - role: galaxy/playbook_help
+
     - role: galaxy/systemd_docker_base
 
     - role: custom/matrix-base