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/apps.py

@@ -1,13 +1,24 @@
+import logging
+
 from django.apps import AppConfig
 
 
+logger = logging.getLogger(__name__)
+
+
 class ModerationConfig(AppConfig):
     default_auto_field = "django.db.models.BigAutoField"
     name = "apps.moderation"
     verbose_name = "Content Moderation"
 
     def ready(self):
-        """Initialize state machines for all moderation models."""
+        """Initialize state machines and callbacks for all moderation models."""
+        self._apply_state_machines()
+        self._register_callbacks()
+        self._register_signal_handlers()
+
+    def _apply_state_machines(self):
+        """Apply FSM to all moderation models."""
         from apps.core.state_machine import apply_state_machine
         from .models import (
             EditSubmission,
@@ -48,3 +59,113 @@ class ModerationConfig(AppConfig):
             choice_group="photo_submission_statuses",
             domain="moderation",
         )
+
+    def _register_callbacks(self):
+        """Register FSM transition callbacks for moderation models."""
+        from apps.core.state_machine.registry import register_callback
+        from apps.core.state_machine.callbacks.notifications import (
+            SubmissionApprovedNotification,
+            SubmissionRejectedNotification,
+            SubmissionEscalatedNotification,
+            ModerationNotificationCallback,
+        )
+        from apps.core.state_machine.callbacks.cache import (
+            ModerationCacheInvalidation,
+        )
+        from .models import (
+            EditSubmission,
+            ModerationReport,
+            ModerationQueue,
+            BulkOperation,
+            PhotoSubmission,
+        )
+
+        # EditSubmission callbacks
+        register_callback(
+            EditSubmission, 'status', 'PENDING', 'APPROVED',
+            SubmissionApprovedNotification()
+        )
+        register_callback(
+            EditSubmission, 'status', 'PENDING', 'APPROVED',
+            ModerationCacheInvalidation()
+        )
+        register_callback(
+            EditSubmission, 'status', 'PENDING', 'REJECTED',
+            SubmissionRejectedNotification()
+        )
+        register_callback(
+            EditSubmission, 'status', 'PENDING', 'REJECTED',
+            ModerationCacheInvalidation()
+        )
+        register_callback(
+            EditSubmission, 'status', 'PENDING', 'ESCALATED',
+            SubmissionEscalatedNotification()
+        )
+        register_callback(
+            EditSubmission, 'status', 'PENDING', 'ESCALATED',
+            ModerationCacheInvalidation()
+        )
+
+        # PhotoSubmission callbacks
+        register_callback(
+            PhotoSubmission, 'status', 'PENDING', 'APPROVED',
+            SubmissionApprovedNotification()
+        )
+        register_callback(
+            PhotoSubmission, 'status', 'PENDING', 'APPROVED',
+            ModerationCacheInvalidation()
+        )
+        register_callback(
+            PhotoSubmission, 'status', 'PENDING', 'REJECTED',
+            SubmissionRejectedNotification()
+        )
+        register_callback(
+            PhotoSubmission, 'status', 'PENDING', 'REJECTED',
+            ModerationCacheInvalidation()
+        )
+        register_callback(
+            PhotoSubmission, 'status', 'PENDING', 'ESCALATED',
+            SubmissionEscalatedNotification()
+        )
+
+        # ModerationReport callbacks
+        register_callback(
+            ModerationReport, 'status', '*', '*',
+            ModerationNotificationCallback()
+        )
+        register_callback(
+            ModerationReport, 'status', '*', '*',
+            ModerationCacheInvalidation()
+        )
+
+        # ModerationQueue callbacks
+        register_callback(
+            ModerationQueue, 'status', '*', '*',
+            ModerationNotificationCallback()
+        )
+        register_callback(
+            ModerationQueue, 'status', '*', '*',
+            ModerationCacheInvalidation()
+        )
+
+        # BulkOperation callbacks
+        register_callback(
+            BulkOperation, 'status', '*', '*',
+            ModerationNotificationCallback()
+        )
+        register_callback(
+            BulkOperation, 'status', '*', '*',
+            ModerationCacheInvalidation()
+        )
+
+        logger.debug("Registered moderation transition callbacks")
+
+    def _register_signal_handlers(self):
+        """Register signal handlers for moderation transitions."""
+        from .signals import register_moderation_signal_handlers
+
+        try:
+            register_moderation_signal_handlers()
+            logger.debug("Registered moderation signal handlers")
+        except Exception as e:
+            logger.warning(f"Could not register moderation signal handlers: {e}")