Add desktop (Electron) and mobile (Expo) showcase apps

New workspace packages for demonstrating design system components:
- Desktop: Electron + Vite app with brand/theme switching
- Mobile: Expo React Native app with brand switching

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/showcase/mobile/package.json

@@ -0,0 +1,41 @@
+{
+  "name": "@dangerousthings/showcase-mobile",
+  "version": "0.0.0",
+  "private": true,
+  "main": "./index.js",
+  "scripts": {
+    "start": "expo start",
+    "android": "expo run:android",
+    "ios": "expo run:ios",
+    "build": "echo 'No build step for Expo dev'",
+    "prebuild": "expo prebuild --clean",
+    "build:android": "expo prebuild --clean --platform android && cd android && ./gradlew assembleRelease && echo 'APK: android/app/build/outputs/apk/release/'",
+    "build:android:debug": "expo prebuild --clean --platform android && cd android && ./gradlew assembleDebug && echo 'Debug APK (requires Metro): android/app/build/outputs/apk/debug/'",
+    "build:ios": "expo prebuild --clean --platform ios && cd ios && xcodebuild -workspace DtShowcase.xcworkspace -scheme DtShowcase -configuration Release -sdk iphoneos -archivePath build/DtShowcase.xcarchive archive",
+    "build:ios:debug": "expo prebuild --clean --platform ios && cd ios && xcodebuild -workspace DtShowcase.xcworkspace -scheme DtShowcase -configuration Debug -sdk iphonesimulator",
+    "build:android:cloud": "eas build -p android --profile preview",
+    "build:ios:cloud": "eas build -p ios --profile preview",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@dangerousthings/react-native": "*",
+    "@dangerousthings/tokens": "*",
+    "@react-navigation/native": "^7.1.27",
+    "@react-navigation/native-stack": "^7.9.1",
+    "babel-preset-expo": "^54.0.10",
+    "expo": "~54.0.32",
+    "expo-font": "~14.0.11",
+    "expo-status-bar": "^3.0.9",
+    "react": "19.1.0",
+    "react-native": "0.81.5",
+    "react-native-paper": "^5.14.5",
+    "react-native-safe-area-context": "~5.6.0",
+    "react-native-screens": "~4.16.0",
+    "react-native-svg": "15.12.1"
+  },
+  "devDependencies": {
+    "@babel/core": "^7.25.2",
+    "@types/react": "~19.1.0",
+    "typescript": "^5.8.3"
+  }
+}