ci: pre-install NDK 27.1.12297006 before EAS local build

Gradle's auto-download of the NDK was failing on the runner with
"Archive is not a ZIP archive" — the download was corrupted/unavailable.
Fix by explicitly installing the NDK via sdkmanager after setup-android
so it is present in $ANDROID_HOME before gradlew runs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/build-android.yml

@@ -32,6 +32,9 @@ jobs:
       - name: 🏗 Setup Android SDK
         uses: android-actions/setup-android@v3
 
+      - name: 🏗 Install Android NDK
+        run: yes | sdkmanager "ndk;27.1.12297006"
+
       - name: 🏗 Setup Expo and EAS
         uses: expo/expo-github-action@v8
         with: