fix: ensure cache directory exists in the image

Dockerfile

@@ -96,6 +96,8 @@ ADD ./entrypoint.sh /.
 
 RUN chmod +x /entrypoint.sh
 
+RUN mkdir -p /var/www/app/var/cache /var/www/app/var/log
+
 ENTRYPOINT ["/entrypoint.sh"]
 
 ENV PHP_FPM_USER=www-data \