[ArneBouten]

Fixes #816

• Use the TrayNotifyWnd rect as an obstacle, so the box can't end up under the tray when the UIA search for tray icons comes back empty.
• If no tray is found at all, keep the current position and retry a few times (about 8 s) before using the layout.
• Ignore tray icons that lie inside the notification area. They are already covered by it, and the press animation of the "Show hidden icons" button briefly reports a larger rect, which made the box shift when opening the overflow.
• Only move to a new position once it has been stable for 5 s, as long as the current position is still free. This stops the box from shifting back and forth during short taskbar reflows or when a tray icon briefly disappears (e.g. Google Drive restarting a process every ~20 s here). Moves needed to avoid an overlap still happen right away.

Tested on Windows 11 26H2 (1920×1080, 100%, left-aligned taskbar): placement is unchanged in normal use, the box returns to the right spot after an Explorer restart, and it no longer shifts when a tray icon is added and removed repeatedly or when the "Show hidden icons" button is clicked.