Use runtime env var for login page message to lower web container startup time (#577)

* Use runtime env var for loginPageMessage

* Rename VITE_LOGIN_PAGE_MESSAGE to PUBLIC_LOGIN_PAGE_MESSAGE in .env.example

* Move docker image `npm run build` step into Dockerfile

* Remove comment from web Dockerfile

web/entrypoint.sh

@@ -1,4 +1,3 @@
-npm run build
 if [ `id -u` -eq 0 ] && [ -n "$PUID" ] && [ -n "$PGID" ]; then
     exec setpriv --reuid $PUID --regid $PGID --clear-groups node /usr/src/app/build/index.js
 else