Fix connection logs: real-time status.log parsing

Root cause: listConnLogs only read from db.json which was never
populated (background sync silently failed due to Status check and
broken regex).

Fix approach: read status.log directly in API handlers — no DB
dependency, works immediately when OpenVPN is running.

Changes:
  api/router.go:
  - listConnLogs: parse status.log from all instances in real-time,
    merge with historical DB entries for disconnected sessions
  - dashboard: same real-time approach for recent_conn_logs

  pkg/openvpn/manager.go:
  - Fix regex for status-version 3 format (11 fields):
    CLIENT_LIST,CN,RealAddr,VPNAddr,IPv6,BytesRecv,BytesSent,ConnectedSince,...
    Old regex assumed wrong field order (CN,ConnectedSince,RealAddr)
  - Add parseConnTime() helper supporting multiple time formats

  internal/service/service.go:
  - Remove Status=='running' check (was blocking sync for all instances)
  - Add log.Printf debug output for sync operations
  - Add 'log' import

  internal/store/store.go:
  - Add ListActiveConns(instanceID) for background sync
  - Add UpdateActiveConnStats() for traffic updates without flush

backend/internal/service/service.go

@@ -8,6 +8,7 @@ import (
 	"encoding/hex"
 	"fmt"
 	"io"
+	"log"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -51,14 +52,15 @@ func (s *Service) StartStatusSync() {
 func (s *Service) syncAllInstanceStatus() {
 	instances := s.Store.ListInstances()
 	for _, in := range instances {
-		if in.Status != "running" {
-			continue
-		}
+		// 不检查 Status 字段，直接尝试读 status.log。
+		// OpenVPN 运行时会自动写 status.log，读到就同步。
 		statusPath := filepath.Join(s.Cfg.InstanceDir(in.Name), "status.log")
 		entries, err := s.Ovm.ParseStatus(statusPath)
 		if err != nil {
-			continue // 文件不存在或解析失败,跳过
+			// 文件不存在或解析失败,跳过
+			continue
 		}
+		log.Printf("[status-sync] instance=%s entries=%d", in.Name, len(entries))
 		// 构建当前在线 CN 集合
 		onlineCNs := map[string]bool{}
 		for _, e := range entries {
@@ -74,6 +76,7 @@ func (s *Service) syncAllInstanceStatus() {
 					BytesOut:    e.BytesSent,
 					ConnectedAt: e.ConnectedAt,
 				})
+				log.Printf("[status-sync] new conn: %s %s %s", e.CommonName, e.RealAddress, e.VPNAddress)
 			} else {
 				// 更新流量统计
 				_ = s.Store.UpdateActiveConnStats(in.ID, e.CommonName, e.BytesRecv, e.BytesSent)
@@ -84,6 +87,7 @@ func (s *Service) syncAllInstanceStatus() {
 			if !onlineCNs[c.CommonName] {
 				now := time.Now()
 				_ = s.Store.CloseActiveConn(in.ID, c.CommonName, now)
+				log.Printf("[status-sync] disconnected: %s", c.CommonName)
 			}
 		}
 	}