fix: check existence of radio.liq file

docker-compose.yml

@@ -52,7 +52,7 @@ services:
     environment:
       LIBRETIME_GENERAL_PUBLIC_URL: http://nginx:8080
     healthcheck:
-      test: liquidsoap --version
+      test: test -f radio.liq
 
   analyzer:
     image: ghcr.io/libretime/libretime-analyzer:${LIBRETIME_VERSION:-latest}