refactor(typing): update handler signatures to use Dict and Any for improved type hinting

steps/vmh/bankverbindungen_sync_event_step.py

@@ -34,7 +34,7 @@ config = {
 }
 
 
-async def handler(event_data: Dict[str, Any], ctx: FlowContext[Any]):
+async def handler(event_data: Dict[str, Any], ctx: FlowContext[Any]) -> None:
     """Zentraler Sync-Handler für Bankverbindungen"""
     
     entity_id = event_data.get('entity_id')