What's new:
- App now shows in Dock (Mac) and Taskbar (Windows) — easy to find and quit
- 🔴 Pointer menu bar / system tray icon with Quit option
- Smoother pointer movement (lerped instead of network-jittery)
- Auto-closes after 10 minutes of inactivity
- Checks for updates on launch
- Teacher can now end all student sessions with one click