ci: add Android build job

.github/workflows/ci.yml

@@ -192,3 +192,35 @@ jobs:
           if target_coverage + 1e-12 < minimum:
               sys.exit(1)
           PY
+
+  android:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+
+      - name: Setup Android SDK
+        uses: android-actions/setup-android@v3
+
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v4
+
+      - name: Install Android SDK packages
+        run: |
+          yes | sdkmanager --licenses >/dev/null
+          sdkmanager --install \
+            "platform-tools" \
+            "platforms;android-36" \
+            "build-tools;36.0.0"
+
+      - name: Android unit tests + debug build
+        working-directory: apps/android
+        run: ./gradlew --no-daemon :app:testDebugUnitTest :app:assembleDebug