Add endpoint to API Server deployments resource to get event stream using client's get_task_result_stream method.

[nerdai]

(The control plane already consumes the stream messages from the Workflow services and emits SSE using FastAPI StreamingResponse)

Implement the equivalent of what we have in workflows:

handler = workflow.run()
async for event in handler.stream_events():
    # do something with event
    pass

for Llama Deploy through the API Server, something like GET http://apiserver.local/my-deployment/events

Acceptance Criteria

• there is an endpoint in the API Server that allows user to get events streamed from a task