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/messaging/definition.py

@@ -3,7 +3,7 @@
 Messaging module definition.
 
 Defines the messaging module including its features, menu items,
-and route configurations.
+route configurations, and self-contained module settings.
 """
 
 from app.modules.base import ModuleDefinition
@@ -17,13 +17,6 @@ def _get_admin_router():
     return admin_router
 
 
-def _get_admin_notifications_router():
-    """Lazy import of admin notifications router to avoid circular imports."""
-    from app.modules.messaging.routes.admin import admin_notifications_router
-
-    return admin_notifications_router
-
-
 def _get_vendor_router():
     """Lazy import of vendor router to avoid circular imports."""
     from app.modules.messaging.routes.vendor import vendor_router
@@ -31,22 +24,18 @@ def _get_vendor_router():
     return vendor_router
 
 
-def _get_vendor_notifications_router():
-    """Lazy import of vendor notifications router to avoid circular imports."""
-    from app.modules.messaging.routes.vendor import vendor_notifications_router
-
-    return vendor_notifications_router
-
-
 # Messaging module definition
 messaging_module = ModuleDefinition(
     code="messaging",
     name="Messaging & Notifications",
     description="Internal messages, customer communication, and notifications.",
+    version="1.0.0",
     features=[
         "customer_messaging",  # Customer communication
         "internal_messages",  # Internal team messages
         "notification_center",  # Notification management
+        "message_attachments",  # File attachments
+        "admin_notifications",  # System admin notifications
     ],
     menu_items={
         FrontendType.ADMIN: [
@@ -59,6 +48,14 @@ messaging_module = ModuleDefinition(
         ],
     },
     is_core=False,
+    # =========================================================================
+    # Self-Contained Module Configuration
+    # =========================================================================
+    is_self_contained=True,
+    services_path="app.modules.messaging.services",
+    models_path="app.modules.messaging.models",
+    schemas_path="app.modules.messaging.schemas",
+    exceptions_path="app.modules.messaging.exceptions",
 )