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/monitoring/__init__.py

@@ -1,25 +1,36 @@
 # app/modules/monitoring/__init__.py
 """
-Monitoring Module - Platform monitoring and system health.
+Monitoring Module - Platform monitoring and observability.
 
-This module provides:
-- Application logs
-- Background tasks monitoring
+This is a self-contained internal module providing:
+- Background task monitoring
 - Import job tracking
-- Platform health metrics
-- Testing hub
-- Code quality tools
+- System capacity monitoring
+- Application logs viewing
+- Platform health checks
 
-Routes:
-- Admin: /api/v1/admin/logs/*, /api/v1/admin/background-tasks/*,
-         /api/v1/admin/tests/*, /api/v1/admin/code-quality/*
-- Vendor: None
-
-Menu Items:
-- Admin: imports, background-tasks, logs, platform-health, testing, code-quality
-- Vendor: None
+Module Structure:
+- models/ - Database models (CapacitySnapshot, AdminNotification, etc.)
+- services/ - Business logic (BackgroundTasksService)
+- schemas/ - Pydantic DTOs
+- routes/ - API and page routes
+- exceptions.py - Module-specific exceptions
 """
 
-from app.modules.monitoring.definition import monitoring_module
+# Use lazy imports to avoid circular import issues
 
-__all__ = ["monitoring_module"]
+
+def __getattr__(name: str):
+    """Lazy import module components to avoid circular imports."""
+    if name == "monitoring_module":
+        from app.modules.monitoring.definition import monitoring_module
+
+        return monitoring_module
+    elif name == "get_monitoring_module_with_routers":
+        from app.modules.monitoring.definition import get_monitoring_module_with_routers
+
+        return get_monitoring_module_with_routers
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+
+
+__all__ = ["monitoring_module", "get_monitoring_module_with_routers"]