feat: enhance Letzshop jobs and order management

- Add job cancellation and retry functionality
- Improve jobs table with better status display
- Add background task improvements
- Update Letzshop order service
- Update documentation

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

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

app/tasks/letzshop_tasks.py

@@ -6,6 +6,7 @@ from datetime import UTC, datetime
 from typing import 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
@@ -207,6 +208,20 @@ def process_historical_import(job_id: int, vendor_id: int):
                 job.status = "failed"
                 job.error_message = f"Letzshop API error: {e}"
                 job.completed_at = datetime.now(UTC)
+
+                # Get vendor name for notification
+                order_service = _get_order_service(db)
+                vendor = order_service.get_vendor(vendor_id)
+                vendor_name = vendor.name if vendor else f"Vendor {vendor_id}"
+
+                # Create admin notification for sync failure
+                admin_notification_service.notify_order_sync_failure(
+                    db=db,
+                    vendor_name=vendor_name,
+                    error_message=f"Historical import failed: {str(e)[:150]}",
+                    vendor_id=vendor_id,
+                )
+
                 db.commit()
 
                 creds_service = _get_credentials_service(db)
@@ -222,6 +237,20 @@ def process_historical_import(job_id: int, vendor_id: int):
                 job.status = "failed"
                 job.error_message = str(e)
                 job.completed_at = datetime.now(UTC)
+
+                # Get vendor name for notification
+                order_service = _get_order_service(db)
+                vendor = order_service.get_vendor(vendor_id)
+                vendor_name = vendor.name if vendor else f"Vendor {vendor_id}"
+
+                # Create admin notification for critical error
+                admin_notification_service.notify_critical_error(
+                    db=db,
+                    error_type="Historical Import",
+                    error_message=f"Import job {job_id} failed for {vendor_name}: {str(e)[:150]}",
+                    details={"job_id": job_id, "vendor_id": vendor_id, "vendor_name": vendor_name},
+                )
+
                 db.commit()
             except Exception as commit_error:
                 logger.error(f"Job {job_id}: Failed to update job status: {commit_error}")