docs(readme): add test coverage summary and commands

Add comprehensive testing documentation to README:
- Test commands for backend (dotnet test)
- Test commands for E2E (playwright)
- Test coverage summary table
- Auth handler tests breakdown

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

README.md

@@ -204,8 +204,13 @@ dotnet build
 dotnet run --project Host
 dotnet watch run --project Host    # Hot reload
 
-# Tests
-dotnet test
+# Tests - Todos
+dotnet test tests/Application.Tests
+dotnet test tests/Domain.Tests
+dotnet test tests/Integration.Tests
+
+# Tests - Solo Auth
+dotnet test tests/Application.Tests --filter "FullyQualifiedName~Auth"
 
 # Migraciones EF Core
 dotnet ef migrations add <Nombre> -p Adapters/Driven/Persistence -s Host
@@ -222,8 +227,44 @@ npx ng serve                          # Desarrollo
 npx ng build --configuration prod     # Producción
 npx ng test                           # Tests unitarios
 npx ng lint                           # Linting
+
+# E2E Tests
+npx playwright test                   # Todos
+npx playwright test auth.spec.ts      # Solo auth
+npx playwright test --reporter=html   # Con reporte HTML
 ```
 
+## Tests Automatizados
+
+### Resumen
+
+| Tipo | Cantidad | Estado |
+|------|----------|--------|
+| Application Tests | 98 | ✅ 100% |
+| Domain Tests | 30 | ✅ 100% |
+| Integration Tests | 5 | ✅ 100% |
+| E2E Tests | 97 | ⚠️ 26% |
+| **Total** | **230** | |
+
+### Tests de Auth (Backend)
+
+| Handler | Tests | Cobertura |
+|---------|-------|-----------|
+| LoginCommand | 6 | Credenciales válidas/inválidas |
+| RegisterCommand | 8 | Registro, duplicados, validaciones |
+| ResetPasswordCommand | 8 | Reset válido/inválido |
+| ActivateAccountCommand | 10 | Activación, expiración, JWT |
+
+### Tests E2E (Playwright)
+
+| Categoría | Tests | Descripción |
+|-----------|-------|-------------|
+| Autenticación | 15 | Login, registro, reset |
+| Control de Acceso | 16 | Roles Admin/Student |
+| Reglas de Negocio | 16 | Max 3 materias, mismo profesor |
+| Activación | 18 | Flujo completo de activación |
+| CRUD | 32 | Estudiantes, inscripciones, compañeros |
+
 ### Docker
 
 ```bash