feat: add Letzshop vendor directory with sync and admin management

- Add LetzshopVendorCache model to store cached vendor data from Letzshop API
- Create LetzshopVendorSyncService for syncing vendor directory
- Add Celery task for background vendor sync
- Create admin page at /admin/letzshop/vendor-directory with:
  - Stats dashboard (total, claimed, unclaimed vendors)
  - Searchable/filterable vendor list
  - "Sync Now" button to trigger sync
  - Ability to create platform vendors from Letzshop cache
- Add API endpoints for vendor directory management
- Add Pydantic schemas for API responses

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

app/tasks/letzshop_tasks.py

@@ -1,15 +1,16 @@
 # app/tasks/letzshop_tasks.py
-"""Background tasks for Letzshop historical order imports."""
+"""Background tasks for Letzshop integration."""
 
 import logging
 from datetime import UTC, datetime
-from typing import Callable
+from typing import Any, Callable
 
 from app.core.database import SessionLocal
 from app.services.admin_notification_service import admin_notification_service
 from app.services.letzshop import LetzshopClientError
 from app.services.letzshop.credentials_service import LetzshopCredentialsService
 from app.services.letzshop.order_service import LetzshopOrderService
+from app.services.letzshop.vendor_sync_service import LetzshopVendorSyncService
 from models.database.letzshop import LetzshopHistoricalImportJob
 
 logger = logging.getLogger(__name__)
@@ -262,3 +263,80 @@ def process_historical_import(job_id: int, vendor_id: int):
                 db.close()
             except Exception as close_error:
                 logger.error(f"Job {job_id}: Error closing database session: {close_error}")
+
+
+# =============================================================================
+# Vendor Directory Sync
+# =============================================================================
+
+
+def sync_letzshop_vendor_directory() -> dict[str, Any]:
+    """
+    Sync Letzshop vendor directory to local cache.
+
+    This task fetches all vendors from Letzshop's public GraphQL API
+    and updates the local letzshop_vendor_cache table.
+
+    Should be run periodically (e.g., daily) via Celery beat.
+
+    Returns:
+        Dictionary with sync statistics.
+    """
+    db = SessionLocal()
+    stats = {}
+
+    try:
+        logger.info("Starting Letzshop vendor directory sync task...")
+
+        sync_service = LetzshopVendorSyncService(db)
+
+        def progress_callback(page: int, fetched: int, total: int):
+            """Log progress during sync."""
+            logger.info(f"Vendor sync progress: page {page}, {fetched}/{total} vendors")
+
+        stats = sync_service.sync_all_vendors(progress_callback=progress_callback)
+
+        logger.info(
+            f"Vendor directory sync completed: "
+            f"{stats.get('created', 0)} created, "
+            f"{stats.get('updated', 0)} updated, "
+            f"{stats.get('errors', 0)} errors"
+        )
+
+        # Send admin notification if there were errors
+        if stats.get("errors", 0) > 0:
+            admin_notification_service.notify_system_info(
+                db=db,
+                title="Letzshop Vendor Sync Completed with Errors",
+                message=(
+                    f"Synced {stats.get('total_fetched', 0)} vendors. "
+                    f"Errors: {stats.get('errors', 0)}"
+                ),
+                details=stats,
+            )
+
+        return stats
+
+    except Exception as e:
+        logger.error(f"Vendor directory sync failed: {e}", exc_info=True)
+
+        # Notify admins of failure
+        try:
+            admin_notification_service.notify_critical_error(
+                db=db,
+                error_type="Vendor Directory Sync",
+                error_message=f"Failed to sync Letzshop vendor directory: {str(e)[:200]}",
+                details={"error": str(e)},
+            )
+            db.commit()
+        except Exception:
+            pass
+
+        raise
+
+    finally:
+        if hasattr(db, "close") and callable(db.close):
+            try:
+                db.close()
+            except Exception as close_error:
+                logger.error(f"Error closing database session: {close_error}")