Gustavo-LVS/AgencyFlowBackEnd — reverse-engineered prompt

Build me a simple JavaScript backend for an agency workflow app called AgencyFlow. I want it to handle the basics an agency would need, like user sign in, clients, projects, tasks, and a way to track each project or task status as it moves through the workflow. It should expose clean API endpoints, validate requests, return clear error messages, and save data properly so the app could be hooked up to a frontend later.

Please keep it organized and easy to understand, with environment based config, sensible routes and controllers, and a short setup guide so I can run it locally without guessing. If it makes sense, add sample seed data and basic API docs or examples for the main endpoints. I do not need anything fancy, just a solid backend foundation that feels production ready enough for a first version. If anything is unclear, use reasonable defaults and look up current docs online if you need to.