Add a native iOS client for relay-based file sharing

The SwiftUI app bundles the Go swarm engine through gomobile, so an iPhone is a real peer using the existing PAKE handshake, chunk verification, and relay fallback. XcodeGen builds the project and devicectl installs it on the paired phone.

apps/ios/build.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+# Build the native iOS app. Usage:
+#   ./build.sh simulator   (default)
+#   ./build.sh device      (signed with the TZGyn team)
+set -euo pipefail
+
+HERE="$(cd "$(dirname "$0")" && pwd)"
+TARGET="${1:-simulator}"
+
+"$HERE/build-go.sh"
+cd "$HERE"
+xcodegen generate
+
+case "$TARGET" in
+  simulator|sim)
+    xcodebuild \
+      -project Share.xcodeproj \
+      -scheme Share \
+      -configuration Debug \
+      -sdk iphonesimulator \
+      -destination 'generic/platform=iOS Simulator' \
+      ARCHS=arm64 ONLY_ACTIVE_ARCH=NO \
+      -derivedDataPath /tmp/share-dd \
+      build
+    ;;
+  device)
+    xcodebuild \
+      -project Share.xcodeproj \
+      -scheme Share \
+      -configuration Debug \
+      -sdk iphoneos \
+      -destination 'generic/platform=iOS' \
+      -allowProvisioningUpdates \
+      -derivedDataPath /tmp/share-dd-device \
+      build
+    ;;
+  *)
+    echo "usage: $0 [simulator|device]" >&2
+    exit 2
+    ;;
+esac