feat: complete marketplace module migration (Phase 6)

Migrates marketplace module to self-contained structure:
- Create app/modules/marketplace/services/ re-exporting from existing locations
- Create app/modules/marketplace/models/ with marketplace & letzshop models
- Create app/modules/marketplace/schemas/ with product & import schemas
- Create app/modules/marketplace/tasks/ with 5 Celery tasks:
  - process_marketplace_import - CSV product import
  - process_historical_import - Letzshop order import
  - sync_vendor_directory - Scheduled daily vendor sync
  - export_vendor_products_to_folder - Multi-language export
  - export_marketplace_products - Admin export
- Create app/modules/marketplace/exceptions.py
- Update definition.py with is_self_contained=True and scheduled_tasks

Celery task migration:
- process_marketplace_import, process_historical_import -> import_tasks.py
- sync_vendor_directory -> sync_tasks.py (scheduled daily at 02:00)
- export_vendor_products_to_folder, export_marketplace_products -> export_tasks.py

Backward compatibility:
- Legacy task files now re-export from new locations
- Remove marketplace/letzshop/export from LEGACY_TASK_MODULES

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

app/modules/marketplace/schemas/__init__.py

@@ -0,0 +1,56 @@
+# app/modules/marketplace/schemas/__init__.py
+"""
+Marketplace module Pydantic schemas.
+
+Re-exports marketplace schemas from the central schemas location.
+Provides a module-local import path while maintaining backwards compatibility.
+
+Usage:
+    from app.modules.marketplace.schemas import (
+        MarketplaceImportJobRequest,
+        MarketplaceProductResponse,
+        MarketplaceProductCreate,
+    )
+"""
+
+from models.schema.marketplace_import_job import (
+    MarketplaceImportJobRequest,
+    AdminMarketplaceImportJobRequest,
+    MarketplaceImportJobResponse,
+    MarketplaceImportJobListResponse,
+)
+from models.schema.marketplace_product import (
+    # Translation schemas
+    MarketplaceProductTranslationSchema,
+    # Base schemas
+    MarketplaceProductBase,
+    # CRUD schemas
+    MarketplaceProductCreate,
+    MarketplaceProductUpdate,
+    # Response schemas
+    MarketplaceProductResponse,
+    MarketplaceProductListResponse,
+    MarketplaceProductDetailResponse,
+    # Import schemas
+    MarketplaceImportRequest,
+    MarketplaceImportResponse,
+)
+
+__all__ = [
+    # Import job schemas
+    "MarketplaceImportJobRequest",
+    "AdminMarketplaceImportJobRequest",
+    "MarketplaceImportJobResponse",
+    "MarketplaceImportJobListResponse",
+    # Product schemas
+    "MarketplaceProductTranslationSchema",
+    "MarketplaceProductBase",
+    "MarketplaceProductCreate",
+    "MarketplaceProductUpdate",
+    "MarketplaceProductResponse",
+    "MarketplaceProductListResponse",
+    "MarketplaceProductDetailResponse",
+    # Import schemas
+    "MarketplaceImportRequest",
+    "MarketplaceImportResponse",
+]