refactor: delete legacy models/database/customer.py

Update the last remaining import in storefront_pages.py to use
app.modules.customers.models, then delete the legacy re-export file.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

models/database/customer.py

@@ -1,23 +0,0 @@
-# models/database/customer.py
-"""
-LEGACY LOCATION - Re-exports from module for backwards compatibility.
-
-The canonical implementation is now in:
-    app/modules/customers/models/customer.py
-
-This file exists to maintain backwards compatibility with code that
-imports from the old location. All new code should import directly
-from the module:
-
-    from app.modules.customers.models import Customer, CustomerAddress
-"""
-
-from app.modules.customers.models.customer import (
-    Customer,
-    CustomerAddress,
-)
-
-__all__ = [
-    "Customer",
-    "CustomerAddress",
-]