Update GitHub Actions to use Java 21 for builds

Build with Java 21 (matching local development environment) while maintaining Java 11 bytecode compatibility via sourceCompatibility setting.

Author: fmontes

.github/workflows/release.yml

@@ -16,11 +16,11 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      - name: Set up JDK 11
+      - name: Set up JDK 21
         uses: actions/setup-java@v4
         with:
-          java-version: '11'
-          distribution: 'temurin'
+          java-version: '21'
+          distribution: 'microsoft'
 
       - name: Grant execute permission for gradlew
         run: chmod +x gradlew