CI: unit tests + debug APK build

.github/workflows/build.yml

@@ -0,0 +1,42 @@
+name: Build & Test
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+      - '1.*'
+  workflow_dispatch:
+
+jobs:
+  build:
+    name: Unit tests & debug APK
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+
+      - name: Setup Gradle with caching
+        uses: gradle/actions/setup-gradle@v4
+
+      - name: Grant execute permission to gradlew
+        run: chmod +x gradlew
+
+      - name: Run unit tests
+        run: ./gradlew --no-daemon testDebugUnitTest
+
+      - name: Build debug APK
+        run: ./gradlew --no-daemon assembleDebug
+
+      - name: Upload debug APK artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: app-debug
+          path: app/build/outputs/apk/debug/app-debug.apk