replace react-nav header hack with scroll edge interaction module

- new expo-scroll-edge-interaction native module (iOS-only) that sets up
  UIScrollEdgeElementContainerInteraction on iOS 26+
- new ScrollEdgeInteractionProvider context and hooks
- Layout.Screen gains `transparentHeader` prop
- Layout.Header.Outer auto-detects transparent mode from context
- List auto-registers scroll view and applies content inset

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/expo-scroll-edge-interaction/ios/ExpoScrollEdgeInteractionModule.swift

@@ -0,0 +1,19 @@
+import ExpoModulesCore
+
+public class ExpoScrollEdgeInteractionModule: Module {
+  public func definition() -> ModuleDefinition {
+    Name("ExpoScrollEdgeInteraction")
+
+    View(ExpoScrollEdgeInteractionView.self) {
+      Prop("nodeHandle") { (view: ExpoScrollEdgeInteractionView, prop: Int?) in
+        view.nodeHandle = prop
+      }
+      Prop("scrollViewTag") { (view: ExpoScrollEdgeInteractionView, prop: Int?) in
+        view.scrollViewTag = prop
+      }
+      Prop("edge") { (view: ExpoScrollEdgeInteractionView, prop: String?) in
+        view.edge = prop
+      }
+    }
+  }
+}