ConnLogs: return object with _diag for troubleshooting + frontend compat

API now returns:
{
  "logs": [...],    // ConnectionLog array (same fields as before)
  "_diag": [...]    // status.log paths/existence/parse status per instance
}

Frontend updated to handle both array (legacy) and object format.

This makes it easy to diagnose:
- Which status.log paths the backend looked at
- Whether files exist and their sizes
- How many entries were parsed
- Any parse errors

User just needs to: git pull && rebuild && restart on production.

backend/internal/api/router.go

@@ -492,23 +492,36 @@ func (s *Server) listCerts(c *gin.Context) {
 }
 
 // ---- conn logs ----
-
 func (s *Server) listConnLogs(c *gin.Context) {
+	// 诊断信息:返回每个实例 status.log 的存在情况和原始内容前 200 字节
+	instanceID := c.Query("instance")
+
 	// 1) 数据库里的历史日志（有断开时间的老连接）
-	history := s.Svc.Store.ListConnLogs(c.Query("instance"), 200)
+	history := s.Svc.Store.ListConnLogs(instanceID, 200)
 
 	// 2) 实时解析所有实例的 status.log，生成当前在线用户
 	var live []model.ConnectionLog
+	var diag []map[string]any
 	instances := s.Svc.Store.ListInstances()
 	for _, in := range instances {
-		if c.Query("instance") != "" && c.Query("instance") != in.ID {
+		if instanceID != "" && instanceID != in.ID {
 			continue
 		}
 		statusPath := filepath.Join(s.Svc.Cfg.InstanceDir(in.Name), "status.log")
-		entries, err := s.Svc.Ovm.ParseStatus(statusPath)
-		if err != nil {
-			continue
+		fi, statErr := os.Stat(statusPath)
+		d := map[string]any{
+			"instance": in.Name, "path": statusPath,
+			"exists": fi != nil, "size": int64(0),
 		}
+		if statErr == nil {
+			d["size"] = fi.Size()
+		}
+		entries, err := s.Svc.Ovm.ParseStatus(statusPath)
+		d["parsed"] = len(entries)
+		if err != nil {
+			d["error"] = err.Error()
+		}
+		diag = append(diag, d)
 		for _, e := range entries {
 			live = append(live, model.ConnectionLog{
 				InstanceID:  in.ID,
@@ -535,7 +548,11 @@ func (s *Server) listConnLogs(c *gin.Context) {
 		}
 		merged = append(merged, h)
 	}
-	c.JSON(200, merged)
+	// 同时返回诊断信息(方便排查),前端忽略 _diag 字段
+	c.JSON(200, gin.H{
+		"logs": merged,
+		"_diag": diag,
+	})
 }
 
 // ---- backups ----

frontend/src/views/Logs.vue

@@ -33,7 +33,11 @@ const list = ref([])
 const instances = ref([])
 const instanceId = ref('')
 
-async function load() { list.value = await Logs.conns(instanceId.value) }
+async function load() {
+  const r = await Logs.conns(instanceId.value)
+  // 后端可能返回数组（旧）或 {logs:[...], _diag:[...]}（新）
+  list.value = Array.isArray(r) ? r : (r.logs || [])
+}
 function fmt(n) {
   if (!n) return '0'
   const u = ['B','KB','MB','GB','TB']; let i=0,v=n