iOS: Duo layout fixes, swipe-up option, fuller backup restore

- DuoRail sits at the bottom of the strip, clear of the back buttons
- Setting to turn off swipe up for Playing Next
- Tighter Now Playing on iPhone Duo (folded and docked), regular phones unchanged
- Bigger stacked stem faders in the Duo deck
- Backup v2 restores song mixes, custom presets and stem playlist covers

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ios/Stemify/UI/Screens/SettingsScreens.swift

@@ -397,7 +397,7 @@ struct BackupCells: View {
 
     var body: some View {
         Button {
-            do { doc = ExportDocument(data: try StemifyExport.capture(g.stemPlaylists, g.settings).encoded()); exporting = true }
+            do { doc = ExportDocument(data: try StemifyExport.capture(g.stemPlaylists, g.playback, g.settings).encoded()); exporting = true }
             catch { message = error.localizedDescription }
         } label: { ValueCell(title: "Export", value: "\(g.stemPlaylists.lists.count) playlists", icon: "square.and.arrow.up", iconBg: 0x007AFF) }
             .themedRow()
@@ -412,9 +412,8 @@ struct BackupCells: View {
                     let scoped = url.startAccessingSecurityScopedResource()
                     defer { if scoped { url.stopAccessingSecurityScopedResource() } }
                     let x = try StemifyExport.decode(Data(contentsOf: url))
-                    let n = g.stemPlaylists.merge(x.playlists)
-                    x.apply(to: g.settings)
-                    message = "Imported \(n) playlist\(n == 1 ? "" : "s") and your sound settings."
+                    let r = x.restore(g.stemPlaylists, g.playback, g.settings)
+                    message = "Restored \(r.playlists) playlist\(r.playlists == 1 ? "" : "s"), \(r.mixes) song mix\(r.mixes == 1 ? "" : "es"), your presets and sound settings."
                 } catch { message = error.localizedDescription }
             }
             .alert("Backup", isPresented: Binding(get: { message != nil }, set: { if !$0 { message = nil } })) {