修复采集服务状态判断：用心跳status字段替代时间推断

src/CncService/Impl/DashboardService.cs

@@ -73,13 +73,8 @@ namespace CncService.Impl
         public object GetCollectorStatus()
         {
             var latest = _collectorHeartbeatRepository.GetLatest("collector-service");
-            bool isRunning = latest != null && latest.LastCollectTime.HasValue &&
-                             (DateTime.Now - latest.LastCollectTime.Value).TotalMinutes < 5;
-            long uptimeSeconds = 0;
-            if (isRunning && latest != null)
-            {
-                uptimeSeconds = latest.UptimeSeconds ?? 0;
-            }
+            bool isRunning = latest != null && latest.Status == "running";
+            long uptimeSeconds = isRunning ? (latest.UptimeSeconds ?? 0) : 0;
             return new { status = isRunning ? "running" : "stopped", uptimeSeconds, lastCollectTime = latest?.LastCollectTime };
         }
     }