Refactor TURN/STUN config:

- Removed ?transport=udp from Nextcloud Talk TURN server definitions
- Dropped --no-tcp-relay to allow TCP fallback
- Removed invalid UDP mapping on TLS port
- Introduced switch between REST secret auth and lt-cred-mech via COTURN_USER_AUTH_ENABLED
- Added user_auth_enabled flag in coturn config for flexibility

See: https://chatgpt.com/share/68d7d601-3558-800f-bc84-00d7e8fc3243

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

@@ -6,14 +6,15 @@ server:
 docker:
   services:
     coturn:
-      image:            "coturn/coturn"
-      version:          "latest"
-      cpus:             1.0
-      mem_reservation:  512m
-      mem_limit:        1g
-      pids_limit:       256
-      network_mode:     host
+      image:              "coturn/coturn"
+      version:            "latest"
+      user_auth_enabled:  false
+      cpus:               1.0
+      mem_reservation:    512m
+      mem_limit:          1g
+      pids_limit:         256
+      network_mode:       host
     redis:
-      enabled:  false
+      enabled:            false
     database: 
-      enabled:  false
+      enabled:            false