fix(scatterlab-prebuild-android): build 잡에 JDK를 설치한다 (#5)

첫 dry-run(run 34550291692)이 Gradle 실행에서 죽었다:

    ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.

리눅스 러너 이미지에 JDK가 없다. `prepare` 잡은 소비자 스모크 테스트가
`./gradlew` 를 쓰느라 `actions/setup-java` 를 들고 있었지만, 정작
ReactAndroid 를 빌드하는 `build` 잡에는 없었다. 같은 버전·배포판(temurin 17)
으로 맞춰 두 잡이 같은 툴체인을 쓰게 한다.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: kdwkr

.github/workflows/scatterlab-prebuild-android.yml

@@ -132,6 +132,14 @@ jobs:
       - uses: ./.github/actions/setup-node
       - uses: ./.github/actions/yarn-install
 
+      # The runner image ships no JDK, and `./gradlew` below needs one. Same version and
+      # distribution as the `prepare` job so both halves of this workflow build against
+      # the same toolchain.
+      - uses: actions/setup-java@v5
+        with:
+          distribution: 'temurin'
+          java-version: '17'
+
       # Without a warm ccache every run is a full C++ rebuild of ReactCommon.
       - name: Restore the Android ccache
         uses: actions/cache/restore@v4