refactor: migrate modules from re-exports to canonical implementations

Move actual code implementations into module directories:
- orders: 5 services, 4 models, order/invoice schemas
- inventory: 3 services, 2 models, 30+ schemas
- customers: 3 services, 2 models, customer schemas
- messaging: 3 services, 2 models, message/notification schemas
- monitoring: background_tasks_service
- marketplace: 5+ services including letzshop submodule
- dev_tools: code_quality_service, test_runner_service
- billing: billing_service
- contracts: definition.py

Legacy files in app/services/, models/database/, models/schema/
now re-export from canonical module locations for backwards
compatibility. Architecture validator passes with 0 errors.

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

app/modules/customers/schemas/__init__.py

@@ -2,27 +2,68 @@
 """
 Customers module Pydantic schemas.
 
-Re-exports customer-related schemas from their source locations.
+This is the canonical location for customer schemas.
+
+Usage:
+    from app.modules.customers.schemas import (
+        CustomerRegister,
+        CustomerUpdate,
+        CustomerResponse,
+    )
 """
 
-from models.schema.customer import (
+from app.modules.customers.schemas.customer import (
+    # Registration & Authentication
     CustomerRegister,
     CustomerUpdate,
-    CustomerLogin,
+    CustomerPasswordChange,
+    # Customer Response
     CustomerResponse,
     CustomerListResponse,
+    # Address
     CustomerAddressCreate,
     CustomerAddressUpdate,
     CustomerAddressResponse,
+    CustomerAddressListResponse,
+    # Preferences
+    CustomerPreferencesUpdate,
+    # Vendor Management
+    CustomerMessageResponse,
+    VendorCustomerListResponse,
+    CustomerDetailResponse,
+    CustomerOrderInfo,
+    CustomerOrdersResponse,
+    CustomerStatisticsResponse,
+    # Admin Management
+    AdminCustomerItem,
+    AdminCustomerListResponse,
+    AdminCustomerDetailResponse,
 )
 
 __all__ = [
+    # Registration & Authentication
     "CustomerRegister",
     "CustomerUpdate",
-    "CustomerLogin",
+    "CustomerPasswordChange",
+    # Customer Response
     "CustomerResponse",
     "CustomerListResponse",
+    # Address
     "CustomerAddressCreate",
     "CustomerAddressUpdate",
     "CustomerAddressResponse",
+    "CustomerAddressListResponse",
+    # Preferences
+    "CustomerPreferencesUpdate",
+    # Vendor Management
+    "CustomerMessageResponse",
+    "VendorCustomerListResponse",
+    "CustomerDetailResponse",
+    "CustomerOrderInfo",
+    "CustomerOrdersResponse",
+    "CustomerStatisticsResponse",
+    # Admin Management
+    "AdminCustomerItem",
+    "AdminCustomerListResponse",
+    "AdminCustomerDetailResponse",
 ]