[client] Keep the UI alive after the last window is destroyed

Since windows are destroyed on close instead of hidden, closing the main
window empties the Wails window map and the default quit-on-last-window
behavior exits the whole tray app on Windows and Linux. Disable it on
both platforms; macOS is already covered by
ApplicationShouldTerminateAfterLastWindowClosed: false.

client/ui/main.go

@@ -277,10 +277,12 @@ func newApplication(onSecondInstance func()) *application.App {
 			ActivationPolicy: application.ActivationPolicyAccessory,
 		},
 		Linux: application.LinuxOptions{
-			ProgramName: "netbird",
+			ProgramName:                   "netbird",
+			DisableQuitOnLastWindowClosed: true,
 		},
 		Windows: application.WindowsOptions{
-			WndProcInterceptor: endSessionInterceptor(),
+			WndProcInterceptor:            endSessionInterceptor(),
+			DisableQuitOnLastWindowClosed: true,
 		},
 		SingleInstance: &application.SingleInstanceOptions{
 			UniqueID: "io.netbird.ui",