ci: add GitHub Actions Android build workflow

.github/workflows/android-build.yml

@@ -0,0 +1,116 @@
+name: MotorSignal Android CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: android-build-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  analyze-and-build:
+    name: Analyze and build Android
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Set up Flutter
+        uses: subosito/flutter-action@v2
+        with:
+          channel: stable
+          cache: true
+
+      - name: Flutter version
+        run: flutter --version
+
+      - name: Get dependencies
+        run: flutter pub get
+
+      - name: Analyze
+        run: flutter analyze
+
+      - name: Run tests
+        run: flutter test
+
+      - name: Build debug APK
+        run: flutter build apk --debug
+
+      - name: Upload debug APK
+        uses: actions/upload-artifact@v5
+        with:
+          name: motorsignal-debug-apk
+          path: build/app/outputs/flutter-apk/app-debug.apk
+          if-no-files-found: error
+          retention-days: 14
+
+  release:
+    name: Build signed release APK
+    runs-on: ubuntu-latest
+    if: github.event_name == 'workflow_dispatch'
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Set up Flutter
+        uses: subosito/flutter-action@v2
+        with:
+          channel: stable
+          cache: true
+
+      - name: Get dependencies
+        run: flutter pub get
+
+      - name: Restore release keystore
+        env:
+          KEYSTORE_BASE64: ${{ secrets.MOTORSIGNAL_KEYSTORE_BASE64 }}
+        run: |
+          test -n "$KEYSTORE_BASE64" || { echo "Missing MOTORSIGNAL_KEYSTORE_BASE64 repository secret"; exit 1; }
+          echo "$KEYSTORE_BASE64" | base64 --decode > android/app/motorsignal-upload-keystore.jks
+
+      - name: Create signing properties
+        env:
+          STORE_PASSWORD: ${{ secrets.MOTORSIGNAL_STORE_PASSWORD }}
+          KEY_PASSWORD: ${{ secrets.MOTORSIGNAL_KEY_PASSWORD }}
+          KEY_ALIAS: ${{ secrets.MOTORSIGNAL_KEY_ALIAS }}
+        run: |
+          test -n "$STORE_PASSWORD" || { echo "Missing MOTORSIGNAL_STORE_PASSWORD repository secret"; exit 1; }
+          test -n "$KEY_PASSWORD" || { echo "Missing MOTORSIGNAL_KEY_PASSWORD repository secret"; exit 1; }
+          test -n "$KEY_ALIAS" || { echo "Missing MOTORSIGNAL_KEY_ALIAS repository secret"; exit 1; }
+          cat > android/key.properties <<EOF
+          storePassword=$STORE_PASSWORD
+          keyPassword=$KEY_PASSWORD
+          keyAlias=$KEY_ALIAS
+          storeFile=app/motorsignal-upload-keystore.jks
+          EOF
+
+      - name: Build release APK
+        run: flutter build apk --release
+
+      - name: Build release App Bundle
+        run: flutter build appbundle --release
+
+      - name: Upload release APK
+        uses: actions/upload-artifact@v5
+        with:
+          name: motorsignal-release-apk
+          path: build/app/outputs/flutter-apk/app-release.apk
+          if-no-files-found: error
+          retention-days: 30
+
+      - name: Upload release App Bundle
+        uses: actions/upload-artifact@v5
+        with:
+          name: motorsignal-release-aab
+          path: build/app/outputs/bundle/release/app-release.aab
+          if-no-files-found: error
+          retention-days: 30