chandansgowda/posture-fix ? reverse-engineered prompt

Build me a small macOS menu bar app called PostureFix that helps me fix my posture while I work using the motion sensors in my AirPods.

I want it to sit in the menu bar, let me start monitoring, ask for the right permissions, and then watch my head position in the background. There should be a simple calibration step where I sit up straight and it remembers that as my baseline. After that, if I start slouching for a few seconds, it should nudge me with an in ear sound, plus optional spoken alert and a macOS notification.

Please also include a basic settings window or menu with controls for sensitivity, how long I need to slouch before it alerts me, cooldown between alerts, and toggles for each alert type. It should show some live status and a simple history view for recent days if that fits. Make it local only, fast, and clean, with a start at login option.

If you need current Apple docs for the headphone motion APIs, look them up online.