How do I approach creating an app that’s runs a local server anytime you start it

My Uncle started a pharmaceutical and we do basically everything manually, recently we started thinking about going digital, and I thought why don't I create a desktop app that handles everything from sales, inventory and automatic price adjustments. I'm good with python and the 3 FE web techs but I don't know how to approach creating the app, it needs to be on multiple computers with one serving as the master (with more rights and privileges) all sales will be synchronized a crossed the whole systems. What tech can I adopt