refactor: remove handlerWrapper and use separate maps in registry

- Remove unnecessary handlerWrapper complexity from push notifications
- Use separate maps for handlers and protection status in registry
- Store handlers directly without indirection layer
- Maintain same instance identity for registered/retrieved handlers
- Preserve all protected handler functionality with cleaner implementation

Changes:
- internal/pushnotif/registry.go: Use separate handlers and protected maps
- push_notifications.go: Remove handlerWrapper, store handlers directly
- Maintain thread-safe operations with simplified code structure

Benefits:
- Reduced memory overhead (no wrapper objects)
- Direct handler storage without type conversion
- Cleaner, more maintainable code
- Same functionality with better performance
- Eliminated unnecessary complexity layer
- Preserved all existing behavior and safety guarantees

internal/pushnotif/types.go

@@ -28,9 +28,3 @@ type RegistryInterface interface {
 	GetRegisteredPushNotificationNames() []string
 	HandleNotification(ctx context.Context, notification []interface{}) bool
 }
-
-// handlerEntry represents a registered handler with its protection status.
-type handlerEntry struct {
-	handler   Handler
-	protected bool
-}