fix: improve onboarding UX and fix order sync error

- Remove redundant 1/4 progress counter from header
- Make step indicators mobile-friendly (smaller circles, hidden labels)
- Add CSV URL help text pointing to Letzshop Admin > API > Export Products
- Fix AttributeError in order sync progress (use correct model attributes)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

static/vendor/js/onboarding.js

@@ -61,7 +61,7 @@ const onboardingTranslations = {
             csv_url_fr: 'French CSV URL',
             csv_url_en: 'English CSV URL',
             csv_url_de: 'German CSV URL',
-            csv_url_help: 'At least one CSV URL is required',
+            csv_url_help: 'Find your CSV URL in Letzshop Admin Panel > API > Export Products',
             default_tax_rate: 'Default Tax Rate (%)',
             delivery_method: 'Delivery Method',
             delivery_package: 'Package Delivery',
@@ -139,7 +139,7 @@ const onboardingTranslations = {
             csv_url_fr: 'URL CSV Français',
             csv_url_en: 'URL CSV Anglais',
             csv_url_de: 'URL CSV Allemand',
-            csv_url_help: 'Au moins une URL CSV est requise',
+            csv_url_help: 'Trouvez votre URL CSV dans Letzshop Admin > API > Exporter Produits',
             default_tax_rate: 'Taux de TVA par Défaut (%)',
             delivery_method: 'Méthode de Livraison',
             delivery_package: 'Livraison Colis',
@@ -217,7 +217,7 @@ const onboardingTranslations = {
             csv_url_fr: 'Französische CSV-URL',
             csv_url_en: 'Englische CSV-URL',
             csv_url_de: 'Deutsche CSV-URL',
-            csv_url_help: 'Mindestens eine CSV-URL ist erforderlich',
+            csv_url_help: 'Finden Sie Ihre CSV-URL im Letzshop Admin-Panel > API > Produkte exportieren',
             default_tax_rate: 'Standard-Steuersatz (%)',
             delivery_method: 'Liefermethode',
             delivery_package: 'Paketlieferung',