Initial commit: Horux Backend API

- API REST para gestion de facturas electronicas mexicanas (CFDI)
- Laravel 9 con autenticacion OAuth 2.0 (Passport)
- Integracion con Syntage, Clerk y Facturama
- 30 modelos Eloquent, 39 controladores
- Documentacion completa en /docs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/TestCase.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Tests;
+
+use Illuminate\Foundation\Testing\TestCase as BaseTestCase;
+
+abstract class TestCase extends BaseTestCase
+{
+    use CreatesApplication;
+}