fix start

Dockerfile

@@ -28,7 +28,7 @@ RUN mkdir -p /data/rooms && \
     chown -R celery:celery /app
 
 # Create and set up startup script
-RUN echo '#!/bin/bash\n\
+RUN printf '#!/bin/bash\n\
 echo "Waiting for database..."\n\
 while ! nc -z db 5432; do\n\
   sleep 0.1\n\
@@ -48,7 +48,7 @@ echo "Creating admin user..."\n\
 flask create-admin\n\
 \n\
 echo "Starting application..."\n\
-exec "$@"' > /app/start.sh && \
+exec "$@"\n' > /app/start.sh && \
     chmod +x /app/start.sh && \
     chown celery:celery /app/start.sh