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/tenancy/services/store_service.py

@@ -439,10 +439,129 @@ class StoreService:
         logger.info(f"Store {store.store_code} set to {status}")
         return store, f"Store {store.store_code} is now {status}"
 
-    # NOTE: Product catalog operations have been moved to catalog module.
-    # Use app.modules.catalog.services.product_service instead.
-    # - add_product_to_catalog -> product_service.create_product
-    # - get_products -> product_service.get_store_products
+    # ========================================================================
+    # Cross-module public API methods
+    # ========================================================================
+
+    def get_stores_by_merchant_id(
+        self, db: Session, merchant_id: int, active_only: bool = False
+    ) -> list[Store]:
+        """
+        Get all stores for a merchant.
+
+        Args:
+            db: Database session
+            merchant_id: Merchant ID
+            active_only: Only return active stores
+
+        Returns:
+            List of Store objects
+        """
+        query = db.query(Store).filter(Store.merchant_id == merchant_id)
+        if active_only:
+            query = query.filter(Store.is_active == True)  # noqa: E712
+        return query.order_by(Store.id).all()
+
+    def get_store_by_code_or_subdomain(
+        self, db: Session, code: str
+    ) -> Store | None:
+        """
+        Get store by store_code or subdomain.
+
+        Args:
+            db: Database session
+            code: Store code or subdomain
+
+        Returns:
+            Store object or None
+        """
+        return (
+            db.query(Store)
+            .filter(
+                (func.upper(Store.store_code) == code.upper())
+                | (func.lower(Store.subdomain) == code.lower())
+            )
+            .first()
+        )
+
+    def get_total_store_count(
+        self, db: Session, active_only: bool = False
+    ) -> int:
+        """
+        Get total count of stores.
+
+        Args:
+            db: Database session
+            active_only: Only count active stores
+
+        Returns:
+            Store count
+        """
+        query = db.query(func.count(Store.id))
+        if active_only:
+            query = query.filter(Store.is_active == True)  # noqa: E712
+        return query.scalar() or 0
+
+    def get_store_count_by_status(
+        self,
+        db: Session,
+        active: bool | None = None,
+        verified: bool | None = None,
+    ) -> int:
+        """
+        Count stores filtered by active/verified status.
+
+        Args:
+            db: Database session
+            active: Filter by active status
+            verified: Filter by verified status
+
+        Returns:
+            Store count matching filters
+        """
+        query = db.query(func.count(Store.id))
+        if active is not None:
+            query = query.filter(Store.is_active == active)
+        if verified is not None:
+            query = query.filter(Store.is_verified == verified)
+        return query.scalar() or 0
+
+    def list_all_stores(self, db: Session, active_only: bool = False) -> list[Store]:
+        """Get all stores, optionally filtering by active status."""
+        query = db.query(Store)
+        if active_only:
+            query = query.filter(Store.is_active == True)  # noqa: E712
+        return query.order_by(Store.id).all()
+
+    def is_letzshop_slug_claimed(self, db: Session, letzshop_slug: str) -> bool:
+        """Check if a Letzshop store slug is already claimed."""
+        return (
+            db.query(Store)
+            .filter(
+                Store.letzshop_store_slug == letzshop_slug,
+                Store.is_active == True,  # noqa: E712
+            )
+            .first()
+            is not None
+        )
+
+    def is_store_code_taken(self, db: Session, store_code: str) -> bool:
+        """Check if a store code already exists."""
+        return (
+            db.query(Store)
+            .filter(Store.store_code == store_code)
+            .first()
+            is not None
+        )
+
+    def is_subdomain_taken(self, db: Session, subdomain: str) -> bool:
+        """Check if a subdomain already exists."""
+        return (
+            db.query(Store)
+            .filter(Store.subdomain == subdomain)
+            .first()
+            is not None
+        )
 
     # Private helper methods
     def _store_code_exists(self, db: Session, store_code: str) -> bool: