Shift Swap Board for Hourly Workers

The idea

I used to work retail and the only way to swap a shift was texting ten coworkers and hoping someone answered before the manager needed a decision. I want a simple board just for one store or restaurant where people post shifts they need covered and others claim them, with the manager only approving the final swap instead of managing the whole search. No scheduling overhaul, just a small tool that sits next to whatever system they already use.