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/billing/services/subscription_service.py

@@ -53,17 +53,16 @@ class SubscriptionService:
         Raises:
             ResourceNotFoundException: If store not found or has no platform
         """
-        from app.modules.tenancy.models import Store, StorePlatform
+        from app.modules.tenancy.services.platform_service import platform_service
+        from app.modules.tenancy.services.store_service import store_service
 
-        store = db.query(Store).filter(Store.id == store_id).first()
+        store = store_service.get_store_by_id_optional(db, store_id)
         if not store or not store.merchant_id:
             raise ResourceNotFoundException("Store", str(store_id))
-        sp = db.query(StorePlatform.platform_id).filter(
-            StorePlatform.store_id == store_id
-        ).first()
-        if not sp:
+        platform_id = platform_service.get_primary_platform_id_for_store(db, store_id)
+        if not platform_id:
             raise ResourceNotFoundException("StorePlatform", f"store_id={store_id}")
-        return store.merchant_id, sp[0]
+        return store.merchant_id, platform_id
 
     def get_store_code(self, db: Session, store_id: int) -> str:
         """Get the store_code for a given store_id.
@@ -71,9 +70,9 @@ class SubscriptionService:
         Raises:
             ResourceNotFoundException: If store not found
         """
-        from app.modules.tenancy.models import Store
+        from app.modules.tenancy.services.store_service import store_service
 
-        store = db.query(Store).filter(Store.id == store_id).first()
+        store = store_service.get_store_by_id_optional(db, store_id)
         if not store:
             raise ResourceNotFoundException("Store", str(store_id))
         return store.store_code
@@ -175,9 +174,10 @@ class SubscriptionService:
             The merchant subscription, or None if the store, merchant,
             or platform cannot be resolved.
         """
-        from app.modules.tenancy.models import Store
+        from app.modules.tenancy.services.platform_service import platform_service
+        from app.modules.tenancy.services.store_service import store_service
 
-        store = db.query(Store).filter(Store.id == store_id).first()
+        store = store_service.get_store_by_id_optional(db, store_id)
         if not store:
             return None
 
@@ -185,17 +185,7 @@ class SubscriptionService:
         if merchant_id is None:
             return None
 
-        # Get platform_id from store
-        platform_id = getattr(store, "platform_id", None)
-        if platform_id is None:
-            from app.modules.tenancy.models import StorePlatform
-            sp = (
-                db.query(StorePlatform.platform_id)
-                .filter(StorePlatform.store_id == store_id)
-                .first()
-            )
-            platform_id = sp[0] if sp else None
-
+        platform_id = platform_service.get_primary_platform_id_for_store(db, store_id)
         if platform_id is None:
             return None
 
@@ -394,5 +384,60 @@ class SubscriptionService:
         return subscription
 
 
+    # =========================================================================
+    # Cross-module public API methods
+    # =========================================================================
+
+    def get_active_subscription_platform_ids(
+        self, db: Session, merchant_id: int
+    ) -> list[int]:
+        """
+        Get platform IDs where merchant has active subscriptions.
+
+        Args:
+            db: Database session
+            merchant_id: Merchant ID
+
+        Returns:
+            List of platform IDs with active subscriptions
+        """
+        active_statuses = [
+            SubscriptionStatus.ACTIVE,
+            SubscriptionStatus.TRIAL,
+        ]
+        results = (
+            db.query(MerchantSubscription.platform_id)
+            .filter(
+                MerchantSubscription.merchant_id == merchant_id,
+                MerchantSubscription.status.in_(active_statuses),
+            )
+            .all()
+        )
+        return [r[0] for r in results]
+
+    def get_all_active_subscriptions(
+        self, db: Session
+    ) -> list[MerchantSubscription]:
+        """
+        Get all active/trial subscriptions with tier and feature limits.
+
+        Returns:
+            List of MerchantSubscription objects with eager-loaded tier data
+        """
+        active_statuses = [
+            SubscriptionStatus.ACTIVE,
+            SubscriptionStatus.TRIAL,
+        ]
+        return (
+            db.query(MerchantSubscription)
+            .options(
+                joinedload(MerchantSubscription.tier)
+                .joinedload(SubscriptionTier.feature_limits),
+            )
+            .filter(MerchantSubscription.status.in_(active_statuses))
+            .all()
+        )
+
+
 # Singleton instance
 subscription_service = SubscriptionService()