Problem

After minimizing to the tray, then sleeping the machine and losing the network for a while, clicking the Reasonix tray icon does nothing — the icon is still there (selectable via Win+B) but no click responds (#3834).

Root cause

fyne.io/systray dispatches a left-click straight from its Win32 message loop:

nativeLoop → GetMessage/DispatchMessage → wndProc → WM_LBUTTONUP → systrayLeftClick() → tappedLeft()

tappedLeft is our SetOnTapped(func(){ a.showFromTray() }), which runs runtime.WindowShow. When the webview / main thread is wedged (a known post-sleep + dropped-connection state), that call blocks, so wndProc never returns and the tray's message pump freezes — the icon stays registered with the shell (hence selectable) but stops processing any click.

The tray menu items don't hit this: they're already decoupled onto goroutines (for range item.ClickedCh). The left-tap handler was the last callback still running on the message loop.

Fix

Dispatch showFromTray on a goroutine so wndProc returns immediately and the pump never blocks — matching the menu-item pattern. A wedged WindowShow then leaks a short-lived goroutine at worst (it completes when the webview recovers) instead of freezing the whole tray.

Test

No unit test — this is a threading fix on a third-party Win32 callback (the menu-item decoupling it mirrors is likewise untested). Verified cd desktop && go build ./... && go vet ./....

Closes #3834