### BASE=http://127.0.0.1:3000/api
--- GET /api/energy-stats/summary
{"code":0,"data":{"cabinet_count":3,"estimated_cost":0.0,"month_energy":0,"online_count":3,"today_energy":0},"message":"ok"}
[HTTP 200]

--- GET /api/energy-stats/cabinets
{"code":"DATABASE_ERROR","message":"服务器内部错误"}
[HTTP 500]

--- GET /api/energy-stats/projects
{"code":0,"data":[{"cabinet_count":1,"month_energy":0,"name":"联调测试项目","project_id":1,"today_energy":0},{"cabinet_count":2,"month_energy":0,"name":"能耗验证临时项目","project_id":2,"today_energy":0}],"message":"ok"}
[HTTP 200]

--- GET /api/energy-stats/trend?granularity=day&range=30
{"code":0,"data":{"granularity":"day","list":[]},"message":"ok"}
[HTTP 200]

--- GET /api/energy-stats/trend?granularity=week&range=30
{"code":0,"data":{"granularity":"week","list":[]},"message":"ok"}
[HTTP 200]

--- GET /api/energy-stats/trend?granularity=month&range=30
{"code":0,"data":{"granularity":"month","list":[]},"message":"ok"}
[HTTP 200]

=== 导出接口（异步任务） ===
{"code":0,"data":{"task_id":1},"message":"导出任务已创建"}
[HTTP 200]