refactor: use compose variable expansion for server port mapping

- Replace static host resolution logic
- Defer HOST/PORT to compose runtime
- Container always binds to 0.0.0.0
- Simplifies normalize_server_host fn
- Removes redundant port fallback logic

Author: danielaskdd

scripts/setup/setup.sh

@@ -312,24 +312,10 @@ normalize_loopback_host_for_compose() {
 }
 
 normalize_server_host_for_compose() {
-  local host="${1:-0.0.0.0}"
-  local publish_host="$host"
-  local publish_port="${ENV_VALUES[PORT]:-9621}"
-
-  case "$publish_host" in
-    localhost)
-      publish_host="127.0.0.1"
-      ;;
-    "")
-      publish_host="0.0.0.0"
-      ;;
-  esac
-
-  if [[ -z "$publish_port" ]]; then
-    publish_port="9621"
-  fi
-
-  LIGHTRAG_COMPOSE_SERVER_PORT_MAPPING="${publish_host}:${publish_port}:9621"
+  # Keep the published bind address/port configurable through compose-time
+  # variable expansion, while forcing the container itself to listen on the
+  # internal service defaults.
+  LIGHTRAG_COMPOSE_SERVER_PORT_MAPPING='${HOST:-0.0.0.0}:${PORT:-9621}:9621'
   NORMALIZED_SERVER_HOST_FOR_COMPOSE="0.0.0.0"
 }