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/cms/services/cms_metrics.py

@@ -147,18 +147,11 @@ class CMSMetricsProvider:
         Aggregates content management data across all stores.
         """
         from app.modules.cms.models import ContentPage, MediaFile, StoreTheme
-        from app.modules.tenancy.models import StorePlatform
+        from app.modules.tenancy.services.platform_service import platform_service
 
         try:
-            # Get all store IDs for this platform using StorePlatform junction table
-            store_ids = (
-                db.query(StorePlatform.store_id)
-                .filter(
-                    StorePlatform.platform_id == platform_id,
-                    StorePlatform.is_active == True,
-                )
-                .subquery()
-            )
+            # Get all store IDs for this platform via platform service
+            store_ids = platform_service.get_store_ids_for_platform(db, platform_id)
 
             # Content pages
             total_pages = (