feat: add self-contained structure to remaining modules

Add exceptions, models, schemas, services directories to modules:

customers:
- exceptions.py, models/, schemas/, services/

inventory:
- exceptions.py, models/, schemas/, services/

messaging:
- exceptions.py, models/, schemas/, services/

monitoring:
- exceptions.py, models/, schemas/, services/

orders:
- exceptions.py, models/, schemas/, services/

payments:
- Updated __init__.py

All modules now have the standard self-contained directory
structure ready for future migration of business logic.

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

app/modules/customers/definition.py

@@ -3,7 +3,7 @@
 Customers module definition.
 
 Defines the customers module including its features, menu items,
-and route configurations.
+route configurations, and self-contained module settings.
 """
 
 from app.modules.base import ModuleDefinition
@@ -28,12 +28,15 @@ def _get_vendor_router():
 customers_module = ModuleDefinition(
     code="customers",
     name="Customer Management",
-    description="Customer database, profiles, and segmentation.",
+    description="Customer database, profiles, addresses, and segmentation.",
+    version="1.0.0",
     features=[
         "customer_view",  # View customer profiles
         "customer_export",  # Export customer data
         "customer_profiles",  # Detailed customer profiles
         "customer_segmentation",  # Customer tagging and segments
+        "customer_addresses",  # Address management
+        "customer_authentication",  # Customer login/registration
     ],
     menu_items={
         FrontendType.ADMIN: [
@@ -44,6 +47,14 @@ customers_module = ModuleDefinition(
         ],
     },
     is_core=True,  # Customers is a core module - customer data is fundamental
+    # =========================================================================
+    # Self-Contained Module Configuration
+    # =========================================================================
+    is_self_contained=True,
+    services_path="app.modules.customers.services",
+    models_path="app.modules.customers.models",
+    schemas_path="app.modules.customers.schemas",
+    exceptions_path="app.modules.customers.exceptions",
 )