add github workflow

.github/workflows/android.yml

@@ -0,0 +1,36 @@
+name: Android CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up JDK 21
+      uses: actions/setup-java@v4
+      with:
+        java-version: '21'
+        distribution: 'temurin'
+        cache: gradle
+
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+
+    - name: Build with Gradle
+      run: ./gradlew build
+
+    - name: Build Debug APK
+      run: ./gradlew assembleDebug
+
+    - name: Upload APK
+      uses: actions/upload-artifact@v4
+      with:
+        name: app-debug
+        path: app/build/outputs/apk/debug/app-debug.apk