Refactor event system to support returnable events

Added support for validating and managing return values in events. Implemented `validate` and `clone` methods in the event base class for event mutation and return handling. Additionally, enhanced error handling, introduced "once" listeners, and improved async execution management in the `EventManager`.

app/src/core/events/index.ts

@@ -1,8 +1,8 @@
-export { Event, NoParamEvent } from "./Event";
+export { Event, NoParamEvent, InvalidEventReturn } from "./Event";
 export {
    EventListener,
    ListenerModes,
    type ListenerMode,
-   type ListenerHandler,
+   type ListenerHandler
 } from "./EventListener";
 export { EventManager, type EmitsEvents, type EventClass } from "./EventManager";