Refactor TURN/STUN handling:

- Split internal/external Coturn for BBB and Nextcloud
- Added dedicated relay port ranges per app
- Updated env and compose overrides for coturn
- Ensure coturn role is loaded conditionally
- Standardize credential/env passing for coturn
@See https://chatgpt.com/share/68d6f376-4878-800f-b4f7-62822caa49ea

roles/web-svc-coturn/config/main.yml

@@ -0,0 +1,14 @@
+username: coturnconsumer
+server:
+  domains:
+    canonical:
+      - "coturn.{{ PRIMARY_DOMAIN }}"
+docker:
+  services:
+    coturn:
+      image:    "coturn/coturn"
+      version:  "latest"
+    redis:
+      enabled:  false
+    database: 
+      enabled:  false