fix(state, server): consolidate duplicate status fields and fix server state response

[eliteprox]

This pull request improves the accuracy and responsiveness of the server's internal state transitions and health reporting. The main focus is on ensuring the pipeline state automatically updates based on client and stream activity, and on cleaning up the health status payload for clarity and consistency.

State transition improvements:

• The internal pipeline state now automatically transitions to OK when there are active streams or an active client, and to IDLE when there is no activity, provided the system is not in an error state. This logic is applied in both the set_active_client and update_active_streams methods for consistency. [1] [2]

• The test for state transitions in test_state_integration.py is updated to expect the state to auto-transition to OK when a stream starts, reflecting the new behavior.

Health status reporting changes:

• The health summary in server.py now consistently reports the status field instead of the legacy state field.

• The get_pipeline_state method's returned dictionary is simplified: it now omits the redundant state, pipeline_state, and additional_info fields, and only includes the status and other essential pipeline indicators.

Before:
GET /stream/status

{
    "status": "IDLE",
    "state": "IDLE",
    "error_message": null,
    "pipeline_ready": true,
    "active_streams": 0,
    "startup_complete": true,
    "pipeline_state": "IDLE",
    "additional_info": {},
    "client_active": false
}

After:
GET /stream/status

{
    "status": "IDLE",
    "pipeline_ready": true,
    "active_streams": 0,
    "startup_complete": true,
    "client_active": false
}

While streaming:

{
    "status": "OK",
    "pipeline_ready": true,
    "active_streams": 1,
    "startup_complete": true,
    "client_active": true,
    "client_running": true,
    "fps": {
        "ingress_video_fps": 15.019144316458277,
        "ingress_audio_fps": 49.99638566362287,
        "egress_video_fps": 15.018221790956062,
        "egress_audio_fps": 49.9960214019784
    },
    "current_params": {
        "subscribe_url": "https://10.10.7.61:9995/ai/trickle/stream-vovnap-a426ba36",
        "publish_url": "https://10.10.7.61:9995/ai/trickle/stream-vovnap-a426ba36-out",
        "gateway_request_id": "stream-vovnap-a426ba36"
    }
}