Could you check if grep is installed as a node package via Strapi’s package.json?
If not, maybe you’d need to install it globally in npm
Another option is to follow this guide
Thats the guide i used to create a deploy ready repository. It doesnt use grep, nor does it sync a local postgress db, but i just start with a deployed strapi instance on Heroku, populate it and while working in my frontend, get the content from the production enviroment.