refactor: clean up legacy models and migrate remaining schemas

Delete empty stub files from models/database/:
- audit.py, backup.py, configuration.py, monitoring.py
- notification.py, payment.py, search.py, task.py

Delete re-export files:
- models/database/subscription.py → app.modules.billing.models
- models/database/architecture_scan.py → app.modules.dev_tools.models
- models/database/test_run.py → app.modules.dev_tools.models
- models/schema/subscription.py → app.modules.billing.schemas
- models/schema/marketplace.py (empty)
- models/schema/monitoring.py (empty)

Migrate schemas to canonical module locations:
- billing.py → app/modules/billing/schemas/
- vendor_product.py → app/modules/catalog/schemas/
- homepage_sections.py → app/modules/cms/schemas/

Keep as CORE (framework-level, used everywhere):
- models/schema/: admin, auth, base, company, email, image, media, team, vendor*
- models/database/: admin*, base, company, email, feature, media, platform*, user, vendor*

Update 30+ files to use canonical import locations.

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

app/api/v1/admin/code_quality.py

@@ -19,7 +19,7 @@ from app.services.code_quality_service import (
     code_quality_service,
 )
 from app.tasks.code_quality_tasks import execute_code_quality_scan
-from models.database.architecture_scan import ArchitectureScan
+from app.modules.dev_tools.models import ArchitectureScan
 from models.database.user import User
 from app.modules.analytics.schemas import CodeQualityDashboardStatsResponse
 

app/api/v1/admin/subscriptions.py

@@ -19,7 +19,7 @@ from app.core.database import get_db
 from app.services.admin_subscription_service import admin_subscription_service
 from app.services.subscription_service import subscription_service
 from models.database.user import User
-from models.schema.billing import (
+from app.modules.billing.schemas import (
     BillingHistoryListResponse,
     BillingHistoryWithVendor,
     SubscriptionStatsResponse,

app/api/v1/admin/vendor_products.py

@@ -22,7 +22,7 @@ from app.core.database import get_db
 from app.services.subscription_service import subscription_service
 from app.services.vendor_product_service import vendor_product_service
 from models.database.user import User
-from models.schema.vendor_product import (
+from app.modules.catalog.schemas import (
     CatalogVendor,
     CatalogVendorsResponse,
     RemoveProductResponse,

app/api/v1/platform/pricing.py

@@ -15,7 +15,7 @@ from sqlalchemy.orm import Session
 from app.core.database import get_db
 from app.exceptions import ResourceNotFoundException
 from app.services.platform_pricing_service import platform_pricing_service
-from models.database.subscription import TierCode
+from app.modules.billing.models import TierCode
 
 router = APIRouter()
 
@@ -188,7 +188,7 @@ def get_tiers(db: Session = Depends(get_db)) -> list[TierResponse]:
         return [_tier_to_response(tier, is_from_db=True) for tier in db_tiers]
 
     # Fallback to hardcoded tiers
-    from models.database.subscription import TIER_LIMITS
+    from app.modules.billing.models import TIER_LIMITS
 
     tiers = []
     for tier_code in TIER_LIMITS:

app/api/v1/vendor/products.py

@@ -26,7 +26,7 @@ from app.modules.catalog.schemas import (
     ProductToggleResponse,
     ProductUpdate,
 )
-from models.schema.vendor_product import (
+from app.modules.catalog.schemas import (
     VendorDirectProductCreate,
     VendorProductCreateResponse,
 )