Specify the flask app in the image

Dockerfile

@@ -14,6 +14,9 @@ RUN apk add --no-cache xmlsec \
  && mkdir /app
 WORKDIR /app
 COPY hiboo /app/hiboo
+COPY migrations /app/migrations
 COPY --from=python_build /usr/local/ /usr/local/
 COPY --from=assets_build /hiboo/static /app/hiboo/static
+
+ENV FLASK_APP hiboo
 CMD gunicorn -w 4 -b :80 --access-logfile - --error-logfile - --preload 'hiboo:create_app()'