[client] Keep tray quit state across an aborted Windows session end

An aborted session end (WM_ENDSESSION with wParam == 0) cleared the
shared shutdown flag, re-enabling hide-on-close cancels and dialogs
while a tray quit was still tearing down. Track the session-end and
tray-quit sources as separate flags; aborting a session end only clears
its own state.

client/ui/main.go

@@ -281,6 +281,9 @@ func newApplication(onSecondInstance func()) *application.App {
 		Linux: application.LinuxOptions{
 			ProgramName: "netbird",
 		},
+		Windows: application.WindowsOptions{
+			WndProcInterceptor: endSessionInterceptor(),
+		},
 		SingleInstance: &application.SingleInstanceOptions{
 			UniqueID: "io.netbird.ui",
 			OnSecondInstanceLaunch: func(_ application.SecondInstanceData) {
@@ -367,6 +370,9 @@ func newMainWindow(app *application.App, prefStore *preferences.Store) *applicat
 
 	// Hide instead of quit on close; "really quit" is reached via tray -> Quit.
 	window.RegisterHook(events.Common.WindowClosing, func(e *application.WindowEvent) {
+		if services.ShuttingDown() {
+			return
+		}
 		e.Cancel()
 		window.Hide()
 	})

client/ui/services/shutdown.go

@@ -0,0 +1,24 @@
+package services
+
+import "sync/atomic"
+
+var (
+	sessionEnding atomic.Bool
+	quitting      atomic.Bool
+)
+
+func BeginSessionEnd() {
+	sessionEnding.Store(true)
+}
+
+func AbortSessionEnd() {
+	sessionEnding.Store(false)
+}
+
+func BeginShutdown() {
+	quitting.Store(true)
+}
+
+func ShuttingDown() bool {
+	return sessionEnding.Load() || quitting.Load()
+}

client/ui/services/windowmanager.go

@@ -154,6 +154,9 @@ func NewWindowManager(app *application.App, mainWindow *application.WebviewWindo
 	})
 	// Hide (not destroy) on close to keep React state; reset to General for a flash-free reopen.
 	s.settings.RegisterHook(events.Common.WindowClosing, func(e *application.WindowEvent) {
+		if ShuttingDown() {
+			return
+		}
 		e.Cancel()
 		s.app.Event.Emit(EventSettingsOpen, "general")
 		s.settings.Hide()
@@ -393,6 +396,9 @@ func (s *WindowManager) CloseWelcome() {
 // OpenError shows the custom error dialog; title/message are pre-localised and ride in the
 // start URL. A second error replaces the open one via SetURL. Singleton, destroyed on close.
 func (s *WindowManager) OpenError(title, message string) {
+	if ShuttingDown() {
+		return
+	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	startURL := errorDialogURL(title, message)

client/ui/shutdown_other.go

@@ -0,0 +1,7 @@
+//go:build !windows && !android && !ios && !freebsd && !js
+
+package main
+
+func endSessionInterceptor() func(hwnd uintptr, msg uint32, wParam, lParam uintptr) (uintptr, bool) {
+	return nil
+}

client/ui/shutdown_windows.go

@@ -0,0 +1,36 @@
+//go:build windows
+
+package main
+
+import (
+	"os"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/ui/services"
+)
+
+const (
+	wmQueryEndSession = 0x0011
+	wmEndSession      = 0x0016
+)
+
+func endSessionInterceptor() func(hwnd uintptr, msg uint32, wParam, lParam uintptr) (uintptr, bool) {
+	return func(_ uintptr, msg uint32, wParam, _ uintptr) (uintptr, bool) {
+		switch msg {
+		case wmQueryEndSession:
+			services.BeginSessionEnd()
+			return 1, true
+		case wmEndSession:
+			if wParam == 0 {
+				services.AbortSessionEnd()
+				return 0, true
+			}
+			log.Info("windows session is ending; exiting immediately")
+			os.Exit(0)
+			return 0, true
+		default:
+			return 0, false
+		}
+	}
+}

client/ui/tray.go

@@ -453,6 +453,7 @@ func (t *Tray) buildMenu() *application.Menu {
 }
 
 func (t *Tray) handleQuit() {
+	services.BeginShutdown()
 	t.profileMu.Lock()
 	if t.switchCancel != nil {
 		t.switchCancel()

client/ui/tray_notify.go

@@ -25,6 +25,9 @@ type sendFn func(notifications.NotificationOptions) error
 // event-dispatch goroutine that panic is fatal process-wide; recover() turns
 // it into a logged no-op.
 func safeSendNotification(send sendFn, what string, opts notifications.NotificationOptions) (err error) {
+	if services.ShuttingDown() {
+		return nil
+	}
 	defer func() {
 		if r := recover(); r != nil {
 			log.Errorf("notify %s: recovered from panic (notification bus unavailable): %v", what, r)