[Bug]: PoI Plugin UI not validating

### Issue description

When uploading a poi.json the validation fails

### Expected behaviour

It should validate just as on the API.

The client builder should call `/api` instead of `/dashboard/api` here https://github.com/iotaledger/node-dashboard/blob/develop/src/services/pluginService.ts#L230

### Actual behaviour

It calls a wrong route and thereby receives a 404 instead of a proper validation repsonse

### Can the issue reliably be reproduced?

Yes

### Steps to reproduce the issue

1. Upload poi.json containing a valid POI

### Errors

```shell
404 -> The given proof of inclusion for the block is invalid.
```

### Duplicate declaration

- [X] I have searched the issues tracker for this issue and there is none

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct