Gunicorn: log to stdout/stderr + preload for crash visibility

- --access-logfile - : access logs to stdout (visible in Nomad)
- --error-logfile -  : error logs to stderr (visible in Nomad)
- --log-level info   : show startup and worker events
- --preload          : load app before forking workers — crashes
                       surface immediately instead of silently dying

Dockerfile

@@ -26,4 +26,4 @@ RUN mkdir -p /app/instance
 
 EXPOSE 5000
 
-CMD ["sh", "-c", "gunicorn --bind ${HOST}:${PORT} --workers 2 --timeout 60 app:app"]
+CMD ["sh", "-c", "gunicorn --bind ${HOST}:${PORT} --workers 2 --timeout 60 --access-logfile - --error-logfile - --log-level info --preload app:app"]