refactor: Move downloaded resources from assets/ to assets_downloaded/

- Changed default download location to assets_downloaded/schematron
- Updated all references in SchematronDownloader, integration, and validator
- Updated postinstall scripts to use new location
- assets_downloaded/ is already in .gitignore to exclude downloaded files from git
- Moved existing downloaded files to new location
- All functionality tested and working correctly

ts/formats/validation/schematron.downloader.ts

@@ -81,7 +81,7 @@ export class SchematronDownloader {
   private cacheDir: string;
   private smartfile: any;
   
-  constructor(cacheDir: string = 'assets/schematron') {
+  constructor(cacheDir: string = 'assets_downloaded/schematron') {
     this.cacheDir = cacheDir;
   }
   
@@ -278,7 +278,7 @@ export const ISO_SCHEMATRON_SKELETONS = {
 /**
  * Download ISO Schematron skeleton files
  */
-export async function downloadISOSkeletons(targetDir: string = 'assets/schematron/iso'): Promise<void> {
+export async function downloadISOSkeletons(targetDir: string = 'assets_downloaded/schematron/iso'): Promise<void> {
   await fs.mkdir(targetDir, { recursive: true });
   
   console.log('Downloading ISO Schematron skeleton files...');

ts/formats/validation/schematron.integration.ts

@@ -75,7 +75,7 @@ export class IntegratedValidator {
     standard: 'EN16931' | 'PEPPOL' | 'XRECHNUNG',
     format: 'UBL' | 'CII'
   ): Promise<string | null> {
-    const basePath = 'assets/schematron';
+    const basePath = 'assets_downloaded/schematron';
     
     // Map standard and format to file pattern
     const patterns: Record<string, Record<string, string>> = {

ts/formats/validation/schematron.validator.ts

@@ -272,19 +272,19 @@ export async function createStandardValidator(
   switch (standard) {
     case 'EN16931':
       // Would load from ConnectingEurope/eInvoicing-EN16931
-      await validator.loadSchematron('assets/schematron/en16931/EN16931-UBL-validation.sch');
+      await validator.loadSchematron('assets_downloaded/schematron/en16931/EN16931-UBL-validation.sch');
       break;
     case 'XRECHNUNG':
       // Would load from itplr-kosit/xrechnung-schematron
-      await validator.loadSchematron('assets/schematron/xrechnung/XRechnung-UBL-validation.sch');
+      await validator.loadSchematron('assets_downloaded/schematron/xrechnung/XRechnung-UBL-validation.sch');
       break;
     case 'PEPPOL':
       // Would load from OpenPEPPOL/peppol-bis-invoice-3
-      await validator.loadSchematron('assets/schematron/peppol/PEPPOL-EN16931-UBL.sch');
+      await validator.loadSchematron('assets_downloaded/schematron/peppol/PEPPOL-EN16931-UBL.sch');
       break;
     case 'FACTURX':
       // Would load from Factur-X specific Schematron
-      await validator.loadSchematron('assets/schematron/facturx/Factur-X-EN16931-validation.sch');
+      await validator.loadSchematron('assets_downloaded/schematron/facturx/Factur-X-EN16931-validation.sch');
       break;
   }