ci: build APK e test su GitHub Actions

Workflow su push a main e avvio manuale: JDK 17, cache Gradle,
suite desktopTest come cancello, assembleDebug e upload dell'APK
come artifact.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -0,0 +1,33 @@
+name: Build
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+
+      - name: Set up Gradle (with cache)
+        uses: gradle/actions/setup-gradle@v4
+
+      - name: Run tests (desktop suite)
+        run: ./gradlew :shared:desktopTest
+
+      - name: Build debug APK
+        run: ./gradlew :app:assembleDebug
+
+      - name: Upload APK artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: intono-debug-apk
+          path: app/build/outputs/apk/debug/app-debug.apk