refactor(arch): eliminate all cross-module model imports in service layer

Enforce MOD-025/MOD-026 rules: zero top-level cross-module model imports
remain in any service file. All 66 files migrated using deferred import
patterns (method-body, _get_model() helpers, instance-cached self._Model)
and new cross-module service methods in tenancy. Documentation updated
with Pattern 6 (deferred imports), migration plan marked complete, and
violations status reflects 84→0 service-layer violations.

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

app/modules/marketplace/services/marketplace_widgets.py

@@ -139,22 +139,18 @@ class MarketplaceWidgetProvider:
         from sqlalchemy.orm import joinedload
 
         from app.modules.marketplace.models import MarketplaceImportJob
-        from app.modules.tenancy.models import StorePlatform
+        from app.modules.tenancy.services.platform_service import platform_service
 
         limit = context.limit if context else 5
 
-        # Get store IDs for this platform
-        store_ids_subquery = (
-            db.query(StorePlatform.store_id)
-            .filter(StorePlatform.platform_id == platform_id)
-            .subquery()
-        )
+        # Get store IDs for this platform via platform service
+        store_ids = platform_service.get_store_ids_for_platform(db, platform_id)
 
         # Get recent imports across all stores in the platform
         jobs = (
             db.query(MarketplaceImportJob)
             .options(joinedload(MarketplaceImportJob.store))
-            .filter(MarketplaceImportJob.store_id.in_(store_ids_subquery))
+            .filter(MarketplaceImportJob.store_id.in_(store_ids))
             .order_by(MarketplaceImportJob.created_at.desc())
             .limit(limit)
             .all()