chore: inference plugin should check service status before sending messages

[louis-jan]

• For now the application does not know when Nitron is ready to use, it is risky to send request to the inference endpoint.
• This service check will give a clue for an UX improvement (loading / error state...)

[louis-jan]

cc @tikikun @vuonghoainam

[louis-jan]

Update:

• Adding available port checking for verification, should emit error to UI if any