Replace manual SOAP authentication with the official nodecfdi library
which properly handles WS-Security signatures for SAT web services.
- Add sat-client.service.ts using Fiel.create() for authentication
- Update sat.service.ts to use new client
- Update fiel.service.ts to return raw certificate data
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>