build JS in prod mode

Were previously building in dev mode to ease debugging

Dockerfile

@@ -35,7 +35,7 @@ COPY client /opt/manifold/client
 WORKDIR /opt/manifold/client
 RUN yarn install
 RUN cat /dev/null > /opt/manifold/client/dist/manifold/ssr/ssr.config.js
-RUN yarn run build:dev
+RUN yarn run build
 
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 # Manifold nginx