fix dockerfile

Dockerfile

@@ -10,6 +10,7 @@ FROM node:slim
 LABEL Maintainer Michael Shihjay Chen <[email protected]>
 WORKDIR /usr/src/app
 ENV NODE_ENV production
+ENV NEXT_PRIVATE_STANDALONE true
 COPY --from=builder /usr/src/app/.next/standalone ./
 COPY --from=builder /usr/src/app/.next/static ./.next/static
 RUN mkdir -p /usr/src/app/trustees