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/orders/definition.py

@@ -3,7 +3,7 @@
 Orders module definition.
 
 Defines the orders module including its features, menu items,
-and route configurations.
+route configurations, and self-contained module settings.
 """
 
 from app.modules.base import ModuleDefinition
@@ -30,7 +30,7 @@ orders_module = ModuleDefinition(
     name="Order Management",
     description=(
         "Order processing, fulfillment tracking, customer checkout, "
-        "and bulk order operations. Uses the payments module for checkout."
+        "invoicing, and bulk order operations. Uses the payments module for checkout."
     ),
     version="1.0.0",
     requires=["payments"],  # Depends on payments module for checkout
@@ -43,6 +43,8 @@ orders_module = ModuleDefinition(
         "shipping_management",  # Carrier integration
         "order_exceptions",  # Order item exception handling
         "customer_checkout",  # Customer checkout flow
+        "invoice_generation",  # Invoice creation
+        "invoice_pdf",  # PDF invoice generation
     ],
     menu_items={
         FrontendType.ADMIN: [
@@ -53,6 +55,14 @@ orders_module = ModuleDefinition(
         ],
     },
     is_core=False,
+    # =========================================================================
+    # Self-Contained Module Configuration
+    # =========================================================================
+    is_self_contained=True,
+    services_path="app.modules.orders.services",
+    models_path="app.modules.orders.models",
+    schemas_path="app.modules.orders.schemas",
+    exceptions_path="app.modules.orders.exceptions",
 )