chore: import upstream snapshot with attribution

.github/workflows/android-build.yml

@@ -0,0 +1,91 @@
+name: Android Build
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'android/**'
+      - '.github/workflows/android-build.yml'
+  pull_request:
+    branches: [main]
+    paths:
+      - 'android/**'
+      - '.github/workflows/android-build.yml'
+
+jobs:
+  build-www:
+    name: Build WebView UI
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: android/www
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'npm'
+          cache-dependency-path: android/www/package-lock.json
+
+      - run: npm ci
+      - run: npm run build
+      - run: cd dist && zip -r ../www.zip .
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: www-zip
+          path: android/www/www.zip
+
+  build-apk:
+    name: Build APK
+    runs-on: ubuntu-latest
+    needs: build-www
+    defaults:
+      run:
+        working-directory: android
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: '21'
+
+      - uses: android-actions/setup-android@v4
+
+      - name: Cache Gradle
+        uses: actions/cache@v5
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: gradle-${{ hashFiles('android/**/*.gradle*', 'android/gradle/libs.versions.toml') }}
+          restore-keys: gradle-
+
+      - name: Build debug APK
+        run: ./gradlew assembleDebug
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: app-debug
+          path: android/app/build/outputs/apk/debug/app-debug.apk
+
+  release:
+    name: Create Release
+    runs-on: ubuntu-latest
+    needs: [build-www, build-apk]
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: app-debug
+
+      - uses: actions/download-artifact@v4
+        with:
+          name: www-zip
+
+      # Release is created manually — artifacts are available for download
+      # To create a tagged release, push a tag: git tag v1.0.0 && git push --tags