refactor(arch): move auth schemas to tenancy module and add cross-module service methods

Move all auth schemas (UserContext, UserLogin, LoginResponse, etc.) from
legacy models/schema/auth.py to app/modules/tenancy/schemas/auth.py per
MOD-019. Update 84 import sites across 14 modules. Legacy file now
re-exports for backwards compatibility.

Add missing tenancy service methods for cross-module consumers:
- merchant_service.get_merchant_by_owner_id()
- merchant_service.get_merchant_count_for_owner()
- admin_service.get_user_by_id() (public, was private-only)
- platform_service.get_active_store_count()

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/orders/routes/api/admin.py

@@ -33,7 +33,7 @@ from app.modules.orders.schemas import (
     ShippingLabelInfo,
 )
 from app.modules.orders.services.order_service import order_service
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 # Base router for orders
 _orders_router = APIRouter(

app/modules/orders/routes/api/admin_exceptions.py

@@ -29,7 +29,7 @@ from app.modules.orders.schemas import (
 from app.modules.orders.services.order_item_exception_service import (
     order_item_exception_service,
 )
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 logger = logging.getLogger(__name__)
 

app/modules/orders/routes/api/store.py

@@ -25,7 +25,7 @@ from app.modules.orders.schemas import (
 )
 from app.modules.orders.services.order_inventory_service import order_inventory_service
 from app.modules.orders.services.order_service import order_service
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 # Base router for orders
 _orders_router = APIRouter(

app/modules/orders/routes/api/store_customer_orders.py

@@ -21,7 +21,7 @@ from app.core.database import get_db
 from app.modules.enums import FrontendType
 from app.modules.orders.services.customer_order_service import customer_order_service
 from app.modules.orders.services.order_metrics import order_metrics_provider
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 logger = logging.getLogger(__name__)
 

app/modules/orders/routes/api/store_exceptions.py

@@ -28,7 +28,7 @@ from app.modules.orders.schemas import (
 from app.modules.orders.services.order_item_exception_service import (
     order_item_exception_service,
 )
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 logger = logging.getLogger(__name__)
 

app/modules/orders/routes/api/store_invoices.py

@@ -51,7 +51,7 @@ from app.modules.orders.schemas import (
     StoreInvoiceSettingsUpdate,
 )
 from app.modules.orders.services.invoice_service import invoice_service
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 store_invoices_router = APIRouter(
     prefix="/invoices",