refactor: use endpoint_id instead of endpoint name for routing

- Update route_payload to use endpoint_id instead of endpoint name
- Update AuthData to expect endpoint_id (int) instead of endpoint (str)
- Update ClientState to track endpoint_id
- Update comfyui client functions to use endpoint_id
- Fetch endpoint info (id + api_key) instead of just api_key

This aligns with the autoscaler changes in AUTO-848 that switched
to ID-based endpoint lookups for improved security and consistency.

workers/openai/test_load.py

@@ -60,7 +60,7 @@ def do_one(endpoint_name: str,
            worker_session):
     try:
         workload = payload.count_workload()
-        route_payload = {"endpoint": endpoint_name, "api_key": endpoint_api_key, "cost": workload}
+        route_payload = {"endpoint_id": endpoint_id, "api_key": endpoint_api_key, "cost": workload}
         headers = {"Authorization": f"Bearer {endpoint_api_key}"}
         start = time.time()
         r0 = route_session.post(urljoin(server_url, "/route/"), json=route_payload, headers=headers, timeout=4)