fix: always emit tribFed and totTrib blocks

[vitormattos]

📝 Summary

Ensure the DPS XML always includes the tribFed and totTrib blocks under trib.

This fixes SEFIN schema rejections where the gateway requires the full trib -> tribMun, tribFed, totTrib sequence even when no federal values were configured.

🧪 How to test

1. Run vendor/bin/phpunit tests/Unit/Xml/XmlBuilderTest.php.
2. Confirm the generated DPS XML always includes <tribFed/> and <totTrib>.
3. Confirm empty tax totals default to 0.00 for federal, state, and municipal percentages.

⚙️ API / Back-end changes

• Always render tribFed in DPS XML output.
• Always render totTrib with 0.00 defaults when values are absent.
• Unit and/or integration tests added – required for backend changes
• Documentation updated (if applicable)

✅ Checklist

• I have read and followed the contribution guide.
• All existing tests pass.
• New tests cover the changed behaviour.
• Commit messages follow Conventional Commits.
• Commits are signed off (git commit -s).

🤖 AI (if applicable)

• The content of this PR was partially or fully generated using AI.