健康报告上传（WebSocket）

wss://mcp.thetahealth.cn/ws/upload-health-report?token=<access_token>&llm_provider=dashscope&llm_api_key=<...>

// 1. 起步
{ "type":"upload_start", "messageId":"<client-uuid>",
  "fileName":"report.pdf", "fileSize":1234567, "query":"分析我的体检报告" }

// 2. 分片（base64 编码）
{ "type":"upload_chunk", "messageId":"...", "chunkIndex":0,
  "totalChunks":12, "data":"<base64>" }

// 3. 结束
{ "type":"upload_end", "messageId":"..." }

// 心跳
{ "type":"ping" }   // 服务端回 { "type":"pong", "timestamp":"..." }

// 查询上传状态
{ "type":"get_status", "messageId":"..." }