fix(ci): use secrets for Docker Hub credentials

Updated the GitHub Actions workflow to use secrets for Docker Hub
username and password instead of hardcoding them. This enhances
security by keeping sensitive information out of the repository.

.github/workflows/test.yml

@@ -18,8 +18,8 @@ jobs:
       - name: Log in to Docker Hub
         uses: docker/login-action@v2
         with:
-          username: "brian247" # Docker Hub username stored in secrets
-          password: "Lian238@Docker" # Docker Hub password stored in secrets
+          username: ${{ secrets.DOCKER_USERNAME }} # Docker Hub username stored in secrets
+          password: ${{ secrets.DOCKER_PASSWORD }} # Docker Hub password stored in secrets
 
       # Step 3: Build Docker image
       - name: Build Docker image