ci: add GitHub Actions workflow to run lint, test, and build APK

.github/workflows/android.yml

@@ -0,0 +1,43 @@
+name: Android CI/CD
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    name: Build & Test Android App
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout Source Code
+        uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: '17'
+          cache: 'gradle'
+
+      - name: Grant Execute Permission for Gradlew
+        run: chmod +x gradlew
+
+      - name: Run Code Style Check (ktlint)
+        run: ./gradlew ktlintCheck
+
+      - name: Run Unit & Integration Tests
+        run: ./gradlew test
+
+      - name: Build Debug APK
+        run: ./gradlew assembleDebug
+
+      - name: Upload Debug APK Artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: hermescontrol-debug-apk
+          path: app/build/outputs/apk/debug/app-debug.apk
+          if-no-files-found: error
+          retention-days: 7