fix: extract target info from nested detections

internal/service/alarm_collector.go

@@ -3,6 +3,7 @@ package service
 import (
 	"database/sql"
 	"encoding/json"
+	"fmt"
 	"log"
 	"sync"
 	"time"
@@ -129,6 +130,19 @@ func (c *AlarmCollector) fetchDeviceAlarms(dev *models.Device) ([]AlarmRecord, e
 				confidence = score
 			}
 		}
+		// Extract from nested detections if top-level fields are empty
+		if dets, ok := a["detections"].([]any); ok && len(dets) > 0 {
+			if objectLabel == "" {
+				objectLabel = fmt.Sprintf("%d 个检测目标", len(dets))
+			}
+			if confidence == 0 {
+				if d0, ok := dets[0].(map[string]any); ok {
+					if s, ok := d0["score"].(float64); ok {
+						confidence = s
+					}
+				}
+			}
+		}
 		durationMs, _ := a["duration_ms"].(float64)
 		alarms = append(alarms, AlarmRecord{
 			ID:          id,