It sounds way too late at this point to worry about stuff like modularization and refactoring. Many of the things you mentioned are certainly important for long

It sounds way too late at this point to worry about stuff like modularization and refactoring. Many of the things you mentioned are certainly important for long-term success, but it sounds like you were hired to impact the nearing release so I'd focus on that first. I would start with the infrastructure stuff like you said, a staging server and CI. If every dev has been relying on local builds, this will probably find a bunch of issues right off the bat. After a stable build environment is established, I would go over the bottlenecks they currently face and work on freeing those up so they can work more efficiently. Since you're so late to the game, you should focus on enabling them to work faster to hit the deadline. All the other methodology and code quality stuff you mentioned can come after that.