fix(bbb): align TURN/STUN configuration with shared coturn service

- added entity_name to vars for consistent docker.service lookup
- switched docker_repository_* vars to use entity_name dynamically
- introduced BBB_TURN_DOMAIN, BBB_TURN_PORT, and BBB_STUN_PORT
  → fallback to web-svc-coturn when BBB_COTURN_ENABLED is false
- updated env.j2 to use new BBB_TURN_* vars instead of hardcoded domain/ports
- cleaned up obsolete comments and spacing

Conversation: https://chatgpt.com/share/68d6c4a8-d524-800f-9592-e8a3407cd721

roles/web-app-bigbluebutton/templates/env.j2

@@ -1,5 +1,7 @@
 # Coturn
 ENABLE_COTURN={{ BBB_COTURN_ENABLED }}
+
+# Credentials
 COTURN_TLS_CERT_PATH={{ BBB_COTURN_TLS_CERT_PATH }}
 COTURN_TLS_KEY_PATH={{ BBB_COTURN_TLS_KEY_PATH }}
 
@@ -49,12 +51,11 @@ EXTERNAL_IPv6={{ networks.internet.ip6 }}
 
 # STUN SERVER
 # stun.freeswitch.org
-STUN_IP={{ networks.internet.ip4 }}
-STUN_PORT={{ ports.public.stun[application_id] }}
+STUN_IP={{ BBB_TURN_DOMAIN }}
+STUN_PORT={{ BBB_STUN_PORT }}
 
 # TURN SERVER
-# uncomment and adjust following two lines to add an external TURN server
-TURN_SERVER=turns:{{ domain }}:{{ ports.public.turn[application_id] }}?transport=tcp
+TURN_SERVER=turns:{{ BBB_TURN_DOMAIN }}:{{ BBB_TURN_PORT }}?transport=tcp
 TURN_SECRET={{ BBB_TURN_SECRET }}
 
 # Allowed SIP IPs
@@ -63,7 +64,6 @@ TURN_SECRET={{ BBB_TURN_SECRET }}
 # Hint: if you want to allow requests from every IP, you can use 0.0.0.0/0
 SIP_IP_ALLOWLIST=
 
-
 # ====================================
 # CUSTOMIZATION
 # ====================================