Add iOS app with CarPlay and Siri

SwiftUI port of the Android app under ios/, with CarPlay browse and
Now Playing, Siri play-media intents, and a build-ipa.sh script that
makes an unsigned IPA for sideloading. README gets an iOS section and
the vibecoded disclaimer.

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

ios/scripts/build-ipa.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+# Builds an unsigned Stemify.ipa on a Mac, for re-signing with Sideloadly/AltStore.
+# Uses swiftc directly so it works even when xcodebuild/actool need -runFirstLaunch.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+export PATH=/opt/homebrew/bin:$PATH
+OUT=build; APP=$OUT/Payload/Stemify.app
+rm -rf $OUT && mkdir -p $APP
+SDK=$(xcrun --sdk iphoneos --show-sdk-path)
+
+xcrun -sdk iphoneos swiftc -target arm64-apple-ios17.0 -sdk "$SDK" -O -wmo -swift-version 5 \
+  -module-name Stemify -parse-as-library $(find Stemify -name '*.swift') -o $APP/Stemify
+
+# Info.plist: xcodegen's generated one with the build settings filled in.
+xcodegen generate -q
+sed -e 's/$(DEVELOPMENT_LANGUAGE)/en/; s/$(EXECUTABLE_NAME)/Stemify/; s/$(PRODUCT_BUNDLE_IDENTIFIER)/com.stemify.mobile/' \
+    -e 's/$(PRODUCT_NAME)/Stemify/; s/$(MARKETING_VERSION)/1.0/; s/$(CURRENT_PROJECT_VERSION)/1/' \
+    -e 's/$(PRODUCT_MODULE_NAME)/Stemify/' Stemify/Info.plist > $APP/Info.plist
+P=$APP/Info.plist
+plutil -insert MinimumOSVersion -string 17.0 $P
+plutil -insert CFBundleSupportedPlatforms -json '["iPhoneOS"]' $P
+plutil -insert UIDeviceFamily -json '[1]' $P
+plutil -insert UIRequiredDeviceCapabilities -json '["arm64"]' $P
+plutil -insert DTPlatformName -string iphoneos $P
+plutil -insert CFBundleIcons -json '{"CFBundlePrimaryIcon":{"CFBundleIconFiles":["AppIcon60x60"]}}' $P
+plutil -lint $P
+printf 'APPL????' > $APP/PkgInfo
+
+# Loose icon files, since actool also needs -runFirstLaunch.
+SRC=Stemify/Resources/Assets.xcassets/AppIcon.appiconset/icon.png
+sips -z 120 120 $SRC --out $APP/AppIcon60x60@2x.png >/dev/null
+sips -z 180 180 $SRC --out $APP/AppIcon60x60@3x.png >/dev/null
+
+(cd $OUT && zip -qry Stemify.ipa Payload)
+echo "$OUT/Stemify.ipa"