Update api_service to use WebSockets

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### Describe your improvement idea or feature request

The new JobQueue system in CCSync does not directly tell the status of the Job or its response, but uses a WebSocket instead.
Integrate this to the `api_service.dart` using [web sockets library in Flutter](https://pub.dev/packages/web_socket_channel).

### How would you like to see it implemented?

1. The user adds/deletes/marks as completed, deleted just like earlier, but
2. Websocket is used to get the message/status and shows the relevant Snackbar
Similar to [this](https://github.com/CCExtractor/ccsync/pull/71)

### Put here any screenshots or videos (optional)

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### By submitting this issue, I have confirmed that:

- [X] I have starred the repo ⭐ and watched 👀 it on GitHub and followed the contribution guidelines.

Lisez api_service.dart et comparez le flux WebSocket proposé avec la pull request #71, en utilisant la bibliothèque web_socket_channel référencée dans l’issue. Vérifiez que les actions add, delete et complete fonctionnent toujours et que l’état de JobQueue ou les messages de réponse produisent la Snackbar correspondante.

Rédigé par le modèle d'indexation à partir du texte de l'issue.