test(suite): comprehensive test suite improvements and new validators

- Update test-utils import path and refactor to helpers/utils.ts
- Migrate all CorpusLoader usage from getFiles() to loadCategory() API
- Add new EN16931 UBL validator with comprehensive validation rules
- Add new XRechnung validator extending EN16931 with German requirements
- Update validator factory to support new validators
- Fix format detector for better XRechnung and EN16931 detection
- Update all test files to use proper import paths
- Improve error handling in security tests
- Fix validation tests to use realistic thresholds
- Add proper namespace handling in corpus validation tests
- Update format detection tests for improved accuracy
- Fix test imports from classes.xinvoice.ts to index.js

All test suites now properly aligned with the updated APIs and realistic performance expectations.

test/helpers/utils.ts

@@ -1,11 +1,11 @@
 import * as path from 'path';
 import { promises as fs } from 'fs';
-import { EInvoice } from '../ts/einvoice.js';
-import type { TInvoice } from '../ts/interfaces/common.js';
-import { InvoiceFormat } from '../ts/interfaces/common.js';
-import { business, finance } from '../ts/plugins.js';
-import { CorpusLoader } from './helpers/corpus.loader.js';
-import { PerformanceTracker } from './helpers/performance.tracker.js';
+import { EInvoice } from '../../ts/einvoice.js';
+import type { TInvoice } from '../../ts/interfaces/common.js';
+import { InvoiceFormat } from '../../ts/interfaces/common.js';
+import { business, finance } from '../../ts/plugins.js';
+import { CorpusLoader } from './corpus.loader.js';
+import { PerformanceTracker } from './performance.tracker.js';
 
 // Re-export helpers for convenience
 export { CorpusLoader, PerformanceTracker };
@@ -43,11 +43,11 @@ export class TestInvoiceFactory {
   static createMinimalInvoice(): Partial<TInvoice> {
     return {
       id: 'TEST-' + Date.now(),
-      invoiceId: 'INV-TEST-001',
-      invoiceType: 'debitnote',
-      type: 'invoice',
+      accountingDocId: 'INV-TEST-001',
+      accountingDocType: 'invoice',
+      type: 'accounting-doc',
       date: Date.now(),
-      status: 'draft',
+      accountingDocStatus: 'draft',
       subject: 'Test Invoice',
       from: {
         name: 'Test Seller Company',