feat(state-machine): add comprehensive callback system for transitions

Extend state machine module with callback infrastructure including:
- Pre/post/error transition callbacks with registry
- Signal-based transition notifications
- Callback configuration and monitoring support
- Helper functions for callback registration
- Improved park ride count updates with FSM integration

backend/apps/moderation/models.py

@@ -9,6 +9,11 @@ This module contains models for the ThrillWiki moderation system, including:
 - BulkOperation: Administrative bulk operations
 
 All models use pghistory for change tracking and TrackedModel base class.
+
+Callback System Integration:
+All FSM-enabled models in this module support the callback system.
+Callbacks for notifications, cache invalidation, and related updates
+are registered via the callback configuration defined in each model's Meta class.
 """
 
 from typing import Any, Dict, Optional, Union
@@ -29,6 +34,35 @@ from apps.core.state_machine import RichFSMField, StateMachineMixin
 UserType = Union[AbstractBaseUser, AnonymousUser]
 
 
+# Lazy callback imports to avoid circular dependencies
+def _get_notification_callbacks():
+    """Lazy import of notification callbacks."""
+    from apps.core.state_machine.callbacks.notifications import (
+        SubmissionApprovedNotification,
+        SubmissionRejectedNotification,
+        SubmissionEscalatedNotification,
+        ModerationNotificationCallback,
+    )
+    return {
+        'approved': SubmissionApprovedNotification,
+        'rejected': SubmissionRejectedNotification,
+        'escalated': SubmissionEscalatedNotification,
+        'moderation': ModerationNotificationCallback,
+    }
+
+
+def _get_cache_callbacks():
+    """Lazy import of cache callbacks."""
+    from apps.core.state_machine.callbacks.cache import (
+        CacheInvalidationCallback,
+        ModerationCacheInvalidation,
+    )
+    return {
+        'generic': CacheInvalidationCallback,
+        'moderation': ModerationCacheInvalidation,
+    }
+
+
 # ============================================================================
 # Original EditSubmission Model (Preserved)
 # ============================================================================