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/billing/routes/api/admin.py

@@ -35,7 +35,7 @@ from app.modules.billing.services import (
     subscription_service,
 )
 from app.modules.enums import FrontendType
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 logger = logging.getLogger(__name__)
 

app/modules/billing/routes/api/admin_features.py

@@ -28,7 +28,7 @@ from app.modules.billing.schemas import (
 from app.modules.billing.services.feature_aggregator import feature_aggregator
 from app.modules.billing.services.feature_service import feature_service
 from app.modules.enums import FrontendType
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 admin_features_router = APIRouter(
     prefix="/features",

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

@@ -23,7 +23,7 @@ from app.modules.billing.schemas.billing import (
 )
 from app.modules.billing.services import billing_service, subscription_service
 from app.modules.enums import FrontendType
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 logger = logging.getLogger(__name__)
 

app/modules/billing/routes/api/store_addons.py

@@ -22,7 +22,7 @@ from app.core.config import settings
 from app.core.database import get_db
 from app.modules.billing.services import billing_service
 from app.modules.enums import FrontendType
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 store_addons_router = APIRouter(
     prefix="/addons",

app/modules/billing/routes/api/store_checkout.py

@@ -34,7 +34,7 @@ from app.modules.billing.schemas.billing import (
 from app.modules.billing.services import billing_service
 from app.modules.billing.services.subscription_service import subscription_service
 from app.modules.enums import FrontendType
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 store_checkout_router = APIRouter(
     dependencies=[Depends(require_module_access("billing", FrontendType.STORE))],

app/modules/billing/routes/api/store_features.py

@@ -38,7 +38,7 @@ from app.modules.billing.services.feature_aggregator import feature_aggregator
 from app.modules.billing.services.feature_service import feature_service
 from app.modules.billing.services.subscription_service import subscription_service
 from app.modules.enums import FrontendType
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 store_features_router = APIRouter(
     prefix="/features",

app/modules/billing/routes/api/store_usage.py

@@ -20,7 +20,7 @@ from app.api.deps import get_current_store_api, require_module_access
 from app.core.database import get_db
 from app.modules.billing.services.usage_service import usage_service
 from app.modules.enums import FrontendType
-from models.schema.auth import UserContext
+from app.modules.tenancy.schemas.auth import UserContext
 
 store_usage_router = APIRouter(
     prefix="/usage",

app/modules/billing/routes/pages/merchant.py

@@ -24,8 +24,8 @@ from app.api.deps import get_current_merchant_from_cookie_or_header
 from app.core.database import get_db
 from app.modules.core.utils.page_context import get_context_for_frontend
 from app.modules.enums import FrontendType
+from app.modules.tenancy.schemas.auth import UserContext
 from app.templates_config import templates
-from models.schema.auth import UserContext
 
 ROUTE_CONFIG = {
     "prefix": "/billing",

app/modules/billing/tests/integration/test_merchant_routes.py

@@ -23,8 +23,8 @@ from app.modules.billing.models import (
     SubscriptionTier,
 )
 from app.modules.tenancy.models import Merchant, Platform, User
+from app.modules.tenancy.schemas.auth import UserContext
 from main import app
-from models.schema.auth import UserContext
 
 # ============================================================================
 # Fixtures