feat: enhance Letzshop order import with EAN matching and stats

- Add historical order import with pagination support
- Add customer_locale, shipping_country_iso, billing_country_iso columns
- Add gtin/gtin_type columns to Product table for EAN matching
- Fix order stats to count all orders server-side (not just visible page)
- Add GraphQL introspection script with tracking workaround tests
- Enrich inventory units with EAN, MPN, SKU, product name
- Add LetzshopOrderStats schema for proper status counts

Migrations:
- a9a86cef6cca: Add locale and country fields to letzshop_orders
- cb88bc9b5f86: Add gtin columns to products table

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

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

app/api/v1/admin/letzshop.py

@@ -361,6 +361,9 @@ def list_vendor_letzshop_orders(
         sync_status=sync_status,
     )
 
+    # Get order stats for all statuses
+    stats = order_service.get_order_stats(vendor_id)
+
     return LetzshopOrderListResponse(
         orders=[
             LetzshopOrderResponse(
@@ -392,6 +395,7 @@ def list_vendor_letzshop_orders(
         total=total,
         skip=skip,
         limit=limit,
+        stats=stats,
     )
 
 
@@ -430,6 +434,10 @@ def trigger_vendor_sync(
     try:
         with creds_service.create_client(vendor_id) as client:
             shipments = client.get_unconfirmed_shipments()
+            logger.info(
+                f"Letzshop sync for vendor {vendor_id}: "
+                f"fetched {len(shipments)} unconfirmed shipments from API"
+            )
 
             orders_imported = 0
             orders_updated = 0
@@ -524,3 +532,118 @@ def list_vendor_letzshop_jobs(
     jobs = [LetzshopJobItem(**job) for job in jobs_data]
 
     return LetzshopJobsListResponse(jobs=jobs, total=total)
+
+
+# ============================================================================
+# Historical Import
+# ============================================================================
+
+
+@router.post(
+    "/vendors/{vendor_id}/import-history",
+)
+def import_historical_orders(
+    vendor_id: int = Path(..., description="Vendor ID"),
+    state: str = Query("confirmed", description="Shipment state to import"),
+    max_pages: int | None = Query(None, ge=1, le=100, description="Max pages to fetch"),
+    match_products: bool = Query(True, description="Match EANs to local products"),
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+):
+    """
+    Import historical orders from Letzshop.
+
+    Fetches all shipments with the specified state (default: confirmed)
+    and imports them into the database. Supports pagination and EAN matching.
+
+    Returns statistics on imported/updated/skipped orders and product matching.
+    """
+    order_service = get_order_service(db)
+    creds_service = get_credentials_service(db)
+
+    try:
+        vendor = order_service.get_vendor_or_raise(vendor_id)
+    except VendorNotFoundError:
+        raise ResourceNotFoundException("Vendor", str(vendor_id))
+
+    # Verify credentials exist
+    try:
+        creds_service.get_credentials_or_raise(vendor_id)
+    except CredentialsNotFoundError:
+        raise ValidationException(
+            f"Letzshop credentials not configured for vendor {vendor.name}"
+        )
+
+    # Fetch all shipments with pagination
+    try:
+        with creds_service.create_client(vendor_id) as client:
+            logger.info(
+                f"Starting historical import for vendor {vendor_id}, state={state}, max_pages={max_pages}"
+            )
+
+            shipments = client.get_all_shipments_paginated(
+                state=state,
+                page_size=50,
+                max_pages=max_pages,
+            )
+
+            logger.info(f"Fetched {len(shipments)} {state} shipments from Letzshop")
+
+            # Import shipments
+            stats = order_service.import_historical_shipments(
+                vendor_id=vendor_id,
+                shipments=shipments,
+                match_products=match_products,
+            )
+
+            db.commit()
+
+            # Update sync status
+            creds_service.update_sync_status(
+                vendor_id,
+                "success",
+                None,
+            )
+
+            logger.info(
+                f"Historical import completed: {stats['imported']} imported, "
+                f"{stats['updated']} updated, {stats['skipped']} skipped"
+            )
+
+            return {
+                "success": True,
+                "message": f"Historical import completed: {stats['imported']} imported, {stats['updated']} updated",
+                "statistics": stats,
+            }
+
+    except LetzshopClientError as e:
+        creds_service.update_sync_status(vendor_id, "failed", str(e))
+        raise ValidationException(f"Letzshop API error: {e}")
+
+
+@router.get(
+    "/vendors/{vendor_id}/import-summary",
+)
+def get_import_summary(
+    vendor_id: int = Path(..., description="Vendor ID"),
+    db: Session = Depends(get_db),
+    current_admin: User = Depends(get_current_admin_api),
+):
+    """
+    Get summary statistics for imported Letzshop orders.
+
+    Returns total orders, unique customers, and breakdowns by state/locale/country.
+    """
+    order_service = get_order_service(db)
+
+    try:
+        order_service.get_vendor_or_raise(vendor_id)
+    except VendorNotFoundError:
+        raise ResourceNotFoundException("Vendor", str(vendor_id))
+
+    summary = order_service.get_historical_import_summary(vendor_id)
+
+    return {
+        "success": True,
+        "summary": summary,
+    }