chore: adiciona job de testes automatizados na pipeline

Job `test` roda em paralelo com `validate`: setup Java 21 (temurin),
cache Gradle, `./gradlew test` com TestContainers (Docker disponível
no runner), publica relatório HTML como artefato em caso de falha.

Programado em par com: Claude IA

Author: joseafilho

.github/workflows/docker-compose-validate.yml

@@ -18,6 +18,29 @@ on:
     paths: *watched-paths
 
 jobs:
+  test:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Java 21
+        uses: actions/setup-java@v4
+        with:
+          java-version: '21'
+          distribution: 'temurin'
+          cache: 'gradle'
+
+      - name: Run tests
+        run: ./gradlew test
+
+      - name: Publish test report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: test-report
+          path: build/reports/tests/test/
+
   validate:
     runs-on: ubuntu-latest
     timeout-minutes: 20