feat(tray): hide window on close and refine tray UX; simplify icon handling
- Intercept CloseRequested to hide instead of exit (keep tray resident)
- Add 'Open Main' menu item; left-click shows menu; reduce tray click logs
- Use default app icon for tray for now; remove runtime PNG decoding
- Drop unused image dependency and tray resources entry
- Prepare path for future macOS template icon under icons/tray/macos
Jason