fix: dashboard metrics 慢查询优化(index+UNIX_TIMESTAMP分组) + 批量升级版本号修复

backend/internal/api/handlers/dashboard.go

@@ -294,28 +294,24 @@ func (h *DashboardHandler) GetMetrics(c *gin.Context) {
 		}
 	}
 
-	// 从 agent_reports 表查最近 N 小时的真实数据（MySQL 聚合）
+	// 从 agent_reports 表查最近 N 小时的真实数据（整数分组，可用索引）
 	since := time.Now().Add(-time.Duration(hours) * time.Hour)
 	type avgPoint struct {
-		Bucket string
-		AvgCPU float64
-		AvgMem float64
+		BucketTS int64
+		AvgCPU   float64
+		AvgMem   float64
 	}
 	var rows []avgPoint
 	h.db.Model(&models.AgentReport{}).
-		Select("DATE_FORMAT(report_time, '%Y-%m-%d %H:00') as bucket, ROUND(AVG(cpu_usage),2) as avg_cpu, ROUND(AVG(mem_usage),2) as avg_mem").
+		Select("UNIX_TIMESTAMP(report_time) DIV 3600 as bucket_ts, ROUND(AVG(cpu_usage),2) as avg_cpu, ROUND(AVG(mem_usage),2) as avg_mem").
 		Where("report_time >= ?", since).
-		Group("bucket").
-		Order("bucket ASC").
+		Group("bucket_ts").
+		Order("bucket_ts ASC").
 		Scan(&rows)
 
 	var metrics []models.MetricData
 	for _, r := range rows {
-		// 手动解析 SQLite strftime 字符串为 time.Time（GORM 无法自动转换） // Logan.Li
-		ts, err := time.ParseInLocation("2006-01-02 15:00", r.Bucket, time.Local)
-		if err != nil {
-			ts = time.Now()
-		}
+		ts := time.Unix(r.BucketTS*3600, 0)
 		metrics = append(metrics,
 			models.MetricData{Name: "cpu", Value: r.AvgCPU, Timestamp: ts},
 			models.MetricData{Name: "memory", Value: r.AvgMem, Timestamp: ts},