refactor: move letzshop endpoints to marketplace module and add vendor service tests

Move letzshop-related functionality from tenancy to marketplace module:
- Move admin letzshop routes to marketplace/routes/api/admin_letzshop.py
- Move letzshop schemas to marketplace/schemas/letzshop.py
- Remove letzshop code from tenancy module (admin_vendors, vendor_service)
- Update model exports and imports

Add comprehensive unit tests for vendor services:
- test_company_service.py: Company management operations
- test_platform_service.py: Platform management operations
- test_vendor_domain_service.py: Vendor domain operations
- test_vendor_team_service.py: Vendor team management

Update module definitions:
- billing, messaging, payments: Minor definition updates

Add architecture proposals documentation:
- Module dependency redesign session notes
- Decouple modules implementation plan
- Module decoupling proposal

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

app/modules/tenancy/schemas/__init__.py

@@ -21,9 +21,6 @@ from app.modules.tenancy.schemas.company import (
 
 # Vendor schemas
 from app.modules.tenancy.schemas.vendor import (
-    LetzshopExportFileInfo,
-    LetzshopExportRequest,
-    LetzshopExportResponse,
     VendorCreate,
     VendorCreateResponse,
     VendorDetailResponse,
@@ -125,9 +122,6 @@ __all__ = [
     "CompanyTransferOwnershipResponse",
     "CompanyUpdate",
     # Vendor
-    "LetzshopExportFileInfo",
-    "LetzshopExportRequest",
-    "LetzshopExportResponse",
     "VendorCreate",
     "VendorCreateResponse",
     "VendorDetailResponse",