fix: 修复Agent指标时区查询

- 统一Agent报告存储与查询的UTC时间边界
- 修复监控大屏、历史图表及离线判断取不到最新数据
- 增加UTC与UTC+8场景回归测试

backend/controller/agent_report_test.go

@@ -2,9 +2,11 @@ package controller
 
 import (
 	"bytes"
+	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"ezops/model"
 
@@ -76,3 +78,68 @@ func TestReceiveReportMatchesExistingAssetByIP(t *testing.T) {
 		t.Fatalf("上报后产生重复资产: count=%d", serverCount)
 	}
 }
+
+func TestGetLatestReportsUsesUTCTimeBoundary(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	db, err := gorm.Open(sqlite.Open("file:agent_latest_utc?mode=memory&cache=shared"), &gorm.Config{
+		Logger: gormlogger.Default.LogMode(gormlogger.Silent),
+	})
+	if err != nil {
+		t.Fatalf("打开测试数据库失败: %v", err)
+	}
+	if err := db.AutoMigrate(&model.Server{}, &model.AgentReport{}); err != nil {
+		t.Fatalf("迁移测试表失败: %v", err)
+	}
+	if err := db.Exec("CREATE TABLE asset_regions (id INTEGER PRIMARY KEY, name TEXT)").Error; err != nil {
+		t.Fatalf("创建区域测试表失败: %v", err)
+	}
+
+	server := model.Server{
+		Hostname:     "c-redis-cluster-3",
+		IP:           "172.19.16.59",
+		AgentVersion: "v2.1.0",
+		AgentStatus:  "online",
+		DiskUsage:    5.56,
+	}
+	if err := db.Create(&server).Error; err != nil {
+		t.Fatalf("创建测试资产失败: %v", err)
+	}
+	// 模拟 Agent 以 UTC 上报，同时应用运行在 UTC+8 时区。 // Logan.Li
+	report := model.AgentReport{
+		Hostname:   server.Hostname,
+		CPUUsage:   12.5,
+		MemUsage:   39.7,
+		CPUCores:   4,
+		ReportTime: time.Now().UTC().Add(-time.Minute),
+	}
+	if err := db.Create(&report).Error; err != nil {
+		t.Fatalf("创建 Agent 报告失败: %v", err)
+	}
+
+	originalLocal := time.Local
+	time.Local = time.FixedZone("UTC+8", 8*60*60)
+	defer func() { time.Local = originalLocal }()
+
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	c.Request = httptest.NewRequest(http.MethodGet, "/api/v1/agent/latest", nil)
+	NewAgentHandler(db, nil, nil).GetLatestReports(c)
+	if recorder.Code != http.StatusOK {
+		t.Fatalf("查询返回码 = %d, body=%s", recorder.Code, recorder.Body.String())
+	}
+
+	var response struct {
+		Code int                         `json:"code"`
+		Data []model.AgentLatestResponse `json:"data"`
+	}
+	if err := json.Unmarshal(recorder.Body.Bytes(), &response); err != nil {
+		t.Fatalf("解析响应失败: %v", err)
+	}
+	if len(response.Data) != 1 {
+		t.Fatalf("主机数量 = %d, body=%s", len(response.Data), recorder.Body.String())
+	}
+	got := response.Data[0]
+	if got.AgentStatus != "online" || got.CPUUsage != 12.5 || got.MemUsage != 39.7 {
+		t.Fatalf("最新指标未命中: status=%q cpu=%.1f mem=%.1f", got.AgentStatus, got.CPUUsage, got.MemUsage)
+	}
+}