web-svc-coturn: Add resource limits and fix docker-compose template

- Set CPU, memory reservation/limit, and PID limit for coturn
- Ensure docker_compose_file_creation_enabled and disable git repo pulling
- Move certificate mounts to volumes and fix env var interpolation in command
- Correct realm and user formatting

See: https://chatgpt.com/share/66f65f18-799c-800a-95f4-b6b26511e9cb

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

@@ -6,8 +6,12 @@ server:
 docker:
   services:
     coturn:
-      image:    "coturn/coturn"
-      version:  "latest"
+      image:            "coturn/coturn"
+      version:          "latest"
+      cpus:             1.0
+      mem_reservation:  512m
+      mem_limit:        1g
+      pids_limit:       256
     redis:
       enabled:  false
     database: