feat: in-app APK update + Gitea CI/CD workflow

- Check /api/app/android/version on launch, prompt user to update
- Download APK and trigger install via FileProvider
- Add Gitea Actions workflow to build release APK and deploy on push
- Add setup script for Act Runner (Java 17 + Android SDK)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-release.yml

@@ -0,0 +1,50 @@
+name: Build & Deploy APK
+
+on:
+  push:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Validate environment
+        run: |
+          echo "Java: $(java --version 2>&1 | head -1)"
+          echo "ANDROID_HOME: $ANDROID_HOME"
+          test -d "$ANDROID_HOME" || { echo "ERROR: ANDROID_HOME not set"; exit 1; }
+
+      - name: Build Release APK
+        run: |
+          chmod +x ./gradlew
+          ./gradlew assembleRelease --no-daemon
+
+      - name: Deploy APK & update version
+        run: |
+          STORAGE="/home/user/itstransport/backend/storage/app/android"
+
+          VERSION_NAME=$(grep 'versionName' app/build.gradle.kts | head -1 | sed 's/.*"\(.*\)".*/\1/')
+          VERSION_CODE=$(grep 'versionCode' app/build.gradle.kts | head -1 | sed 's/[^0-9]*//g')
+
+          APK=$(find app/build/outputs/apk/release -name "*.apk" | head -1)
+          test -n "$APK" || { echo "ERROR: No APK found"; exit 1; }
+
+          cp "$APK" "$STORAGE/app-release.apk"
+
+          COMMIT_MSG=$(git log -1 --pretty=%s | sed 's/"/\\"/g')
+          python3 -c "
+          import json
+          data = {
+              'versionName': '$VERSION_NAME',
+              'versionCode': int('$VERSION_CODE'),
+              'releaseNotes': \"$COMMIT_MSG\"
+          }
+          with open('$STORAGE/version.json', 'w') as f:
+              json.dump(data, f, indent=4, ensure_ascii=False)
+              f.write('\n')
+          "
+
+          echo "Deployed v${VERSION_NAME} (code ${VERSION_CODE}) — $(du -h "$STORAGE/app-release.apk" | cut -f1)"