fix: correct order sync_status and historical import display

- Fix historical import to also update sync_status when it's out of
  sync with letzshop_state (e.g., confirmed orders showing as pending)
- Fix frontend to read stats from response.statistics nested object
- Orders with matching letzshop_state but wrong sync_status now get fixed

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

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

static/admin/js/marketplace-letzshop.js

@@ -469,8 +469,10 @@ function adminMarketplaceLetzshop() {
                     `/admin/letzshop/vendors/${this.selectedVendor.id}/import-history?state=confirmed`
                 );
 
-                this.historicalImportResult = response;
-                this.successMessage = `Historical import complete: ${response.imported} imported, ${response.updated} updated`;
+                // Stats are nested under 'statistics' key
+                this.historicalImportResult = response.statistics || response;
+                const stats = this.historicalImportResult;
+                this.successMessage = `Historical import complete: ${stats.imported} imported, ${stats.updated} updated`;
 
                 marketplaceLetzshopLog.info('Historical import result:', response);