v0.12.0

**Added**
- A system tray icon: closing the window now hides it instead of quitting,
  so a hosted server or P2P room keeps running. Right-click the tray icon
  to actually quit, or turn this off in Settings

**Fixed**
- Restarting the app and hosting a new P2P room could hand out a ticket
  nobody outside your own network could join, if the relay connection
  hadn't finished negotiating yet — hosting now waits for it properly
  instead of guessing a fixed delay