docs(grafana): add gpuWorkloadHistory deep-link endpoint (#824)

[SekiXu]

What type of PR is this?

Docs — OpenAPI spec (document a new endpoint).

Which issue(s) this PR fixes?

Backend track of bigstack-oss/cubecos#824 and bigstack-oss/cubecos#825. Documents the endpoint implemented in cube-cos-api (companion PR on branch feat/824-gpu-workload-history-backend).

What this PR does?

Adds the OpenAPI definition for GET /api/v1/datacenters/{dataCenter}/grafana/gpuWorkloadHistory/{hostname}, which returns the Device dashboard (UID i-device) deep-links for a physical node's GPU Utilization (panel 50) and VRAM (panel 51).

• New path /api/v1/datacenters/{dataCenter}/grafana/gpuWorkloadHistory/{hostname} (tag Grafana, operationId getGrafanaGpuWorkloadHistory), mirroring the existing /grafana/hosts/{hostname} entry.
• New response schema GetGpuWorkloadHistoryLinksResponse with data: { gpuUtilizationUrl, vramUrl, enabled }.

Example 200 response:

{
  "code": 200,
  "data": {
    "gpuUtilizationUrl": "http://example-data-center/grafana/d/i-device/device?orgId=1&var-GPU_HOST=example-node-0&from=now-3h&to=now&viewPanel=50",
    "vramUrl": "http://example-data-center/grafana/d/i-device/device?orgId=1&var-GPU_HOST=example-node-0&from=now-3h&to=now&viewPanel=51",
    "enabled": true
  },
  "msg": "fetch gpu workload history links successfully",
  "status": "ok"
}

Test results (optional)

• yq -o=json -I=4 docs.yaml converts cleanly (validated in the cube-cos-api build container); task generateApiDocs regenerates docs.json with the new endpoint present.
• Endpoint smoke-verified against the live API on test node sky150 (companion cube-cos-api PR): valid node → both URLs + enabled:true; non-existent hostname → enabled:false.

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