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/loyalty/services/program_service.py

@@ -75,9 +75,9 @@ class ProgramService:
 
         Looks up the store's merchant and returns the merchant's program.
         """
-        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:
             return None
 
@@ -89,9 +89,9 @@ class ProgramService:
 
         Looks up the store's merchant and returns the merchant's active program.
         """
-        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:
             return None
 
@@ -140,15 +140,9 @@ class ProgramService:
             StoreNotFoundException: If store not found
         """
         from app.modules.tenancy.exceptions import StoreNotFoundException
-        from app.modules.tenancy.models import Store
+        from app.modules.tenancy.services.store_service import store_service
 
-        store = (
-            db.query(Store)
-            .filter(
-                (Store.store_code == store_code) | (Store.subdomain == store_code)
-            )
-            .first()
-        )
+        store = store_service.get_store_by_code_or_subdomain(db, store_code)
         if not store:
             raise StoreNotFoundException(store_code)
         return store
@@ -168,9 +162,9 @@ class ProgramService:
             StoreNotFoundException: If store not found
         """
         from app.modules.tenancy.exceptions import StoreNotFoundException
-        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 StoreNotFoundException(str(store_id), identifier_type="id")
         return store.merchant_id
@@ -186,12 +180,10 @@ class ProgramService:
         Returns:
             List of active Store objects
         """
-        from app.modules.tenancy.models import Store
+        from app.modules.tenancy.services.store_service import store_service
 
-        return (
-            db.query(Store)
-            .filter(Store.merchant_id == merchant_id, Store.is_active == True)
-            .all()
+        return store_service.get_stores_by_merchant_id(
+            db, merchant_id, active_only=True
         )
 
     def get_program_list_stats(self, db: Session, program) -> dict:
@@ -209,9 +201,9 @@ class ProgramService:
         from sqlalchemy import func
 
         from app.modules.loyalty.models import LoyaltyCard, LoyaltyTransaction
-        from app.modules.tenancy.models import Merchant
+        from app.modules.tenancy.services.merchant_service import merchant_service
 
-        merchant = db.query(Merchant).filter(Merchant.id == program.merchant_id).first()
+        merchant = merchant_service.get_merchant_by_id_optional(db, program.merchant_id)
         merchant_name = merchant.name if merchant else None
 
         total_cards = (
@@ -372,18 +364,16 @@ class ProgramService:
             is_active: Filter by active status
             search: Search by merchant name (case-insensitive)
         """
-        from app.modules.tenancy.models import Merchant
-
-        query = db.query(LoyaltyProgram).join(
-            Merchant, LoyaltyProgram.merchant_id == Merchant.id
-        )
+        query = db.query(LoyaltyProgram)
 
         if is_active is not None:
             query = query.filter(LoyaltyProgram.is_active == is_active)
 
         if search:
-            search_pattern = f"%{search}%"
-            query = query.filter(Merchant.name.ilike(search_pattern))
+            from app.modules.tenancy.services.merchant_service import merchant_service
+            merchants, _ = merchant_service.get_merchants(db, search=search, limit=10000)
+            merchant_ids = [m.id for m in merchants]
+            query = query.filter(LoyaltyProgram.merchant_id.in_(merchant_ids))
 
         total = query.count()
         programs = query.order_by(LoyaltyProgram.created_at.desc()).offset(skip).limit(limit).all()
@@ -720,7 +710,7 @@ class ProgramService:
         from sqlalchemy import func
 
         from app.modules.loyalty.models import LoyaltyCard, LoyaltyTransaction
-        from app.modules.tenancy.models import Store
+        from app.modules.tenancy.services.store_service import store_service
 
         program = self.get_program_by_merchant(db, merchant_id)
 
@@ -834,7 +824,7 @@ class ProgramService:
         )
 
         # Get all stores for this merchant for location breakdown
-        stores = db.query(Store).filter(Store.merchant_id == merchant_id).all()
+        stores = store_service.get_stores_by_merchant_id(db, merchant_id)
 
         location_stats = []
         for store in stores: