refactor: Remove AlertHost and AlertManager from desktop entry point

- Remove `AlertManager` dependency and its initialization within the `Main` composition.
- Remove the `AlertHost` component from the top-level UI tree in `Main.kt`.

desktop/src/main/kotlin/org/meshtastic/desktop/Main.kt

@@ -174,7 +174,6 @@ fun main(args: Array<String>) = application(exitProcessOnExit = false) {
     var isWindowReady by remember { mutableStateOf(false) }
     val appIcon = classpathPainterResource("icon.png")
 
-    val alertManager = remember { koinApp.koin.get<org.meshtastic.core.ui.util.AlertManager>() }
     val desktopPrefs = remember { koinApp.koin.get<DesktopPreferencesDataSource>() }
     val windowState = rememberWindowState()
 
@@ -298,7 +297,6 @@ fun main(args: Array<String>) = application(exitProcessOnExit = false) {
             // preserves remembered state (including the navigation backstack).
             CompositionLocalProvider(LocalAppLocale provides localePref) {
                 AppTheme(darkTheme = isDarkTheme) {
-                    org.meshtastic.core.ui.component.AlertHost(alertManager)
                     DesktopMainScreen(backStack)
                 }
             }