Fix iOS menu text disappearing in navigation headers

Extended the ZStack overlay fix to all iOS navigation header menus
where text labels would disappear when tapping the menu:

- HomeView: "Home" title menu
- PopularView: "Popular" title with icon menu
- TrendingView: Country/flag title menu
- PlaylistsView: Playlist title with thumbnail menu
- ChannelPlaylistView: Playlist title with thumbnail menu
- OpenVideosView: Playback mode picker menu

All menus now use the same pattern as PlaybackSettings:
- Visible static label layer in ZStack
- Invisible Menu overlay with .opacity(0)
- Prevents text disappearing and resizing animations

Shared/Views/OpenVideosView.swift

@@ -144,10 +144,15 @@ struct OpenVideosView: View {
                 Spacer()
             #endif
             #if os(iOS)
-                Menu {
-                    playbackModePicker
-                } label: {
+                ZStack {
                     Text(playbackMode.description)
+
+                    Menu {
+                        playbackModePicker
+                    } label: {
+                        Text(playbackMode.description)
+                            .opacity(0)
+                    }
                 }
             #else
                 playbackModePicker