ios: reorderable tab bar with more tabs, debug log export, AirPlay picker, more room above seeker

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

ios/Stemify/UI/Components/Chrome.swift

@@ -1,4 +1,6 @@
+import AVKit
 import SwiftUI
+import UIKit
 
 let MARGIN: CGFloat = 20
 
@@ -330,3 +332,21 @@ private struct ListRow: ViewModifier {
             }
     }
 }
+
+/// The system AirPlay / Bluetooth output picker. The mix is rendered on the phone, so stem edits keep working over AirPlay.
+struct AirPlayButton: UIViewRepresentable {
+    var tint: UIColor = .label
+    var active: UIColor = .systemBlue
+
+    func makeUIView(context: Context) -> AVRoutePickerView {
+        let v = AVRoutePickerView()
+        v.prioritizesVideoDevices = false
+        v.backgroundColor = .clear
+        return v
+    }
+
+    func updateUIView(_ v: AVRoutePickerView, context: Context) {
+        v.tintColor = tint
+        v.activeTintColor = active
+    }
+}