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/pkg/openvpn/manager.go

@@ -614,7 +614,9 @@ type StatusEntry struct {
 
 var (
 	reHdr  = regexp.MustCompile(`^Updated,([^,]+),`)
-	reCli  = regexp.MustCompile(`^CLIENT_LIST,([^,]+),([^,]+),([^,]+),(\d+),(\d+),`)
+	// status-version 3 CLIENT_LIST 格式（11个字段）:
+	// CLIENT_LIST,CommonName,RealAddress,VirtualAddress,VirtualIPv6,BytesRecv,BytesSent,ConnectedSince,Username,ClientID,PeerID
+	reCli = regexp.MustCompile(`^CLIENT_LIST,([^,]+),([^,]+),([^,]+),([^,]*),(\d+),(\d+),([^,]+),`)
 	reTime = regexp.MustCompile(`^Connected Since,([^,]+),`)
 )
 
@@ -630,14 +632,13 @@ func ParseStatusReader(r io.Reader) ([]StatusEntry, error) {
 			if m == nil {
 				continue
 			}
-			connected, _ := time.Parse("Mon Jan 2 15:04:05 2006", m[2])
 			out = append(out, StatusEntry{
 				CommonName:  m[1],
-				RealAddress: m[3],
-				VPNAddress:  m[4],
-				BytesRecv:   atoi64(m[5]),
-				BytesSent:   atoi64(m[6]),
-				ConnectedAt: connected,
+					RealAddress: m[2],  // RealAddress (IP:port)
+					VPNAddress:  m[3],  // VirtualAddress
+					BytesRecv:   atoi64(m[5]),
+					BytesSent:   atoi64(m[6]),
+					ConnectedAt: parseConnTime(m[7]),
 			})
 		}
 	}
@@ -693,6 +694,33 @@ func atoi64(s string) int64 {
 	return n
 }
 
+// parseConnTime 解析 OpenVPN status.log 中的时间字段。
+// status-version 3 格式: "Mon Jan  2 15:04:05 2006" (注意可能有双空格)
+// 部分版本使用 Unix 时间戳。
+func parseConnTime(s string) time.Time {
+	s = strings.TrimSpace(s)
+	if s == "" {
+		return time.Time{}
+	}
+	// 先尝试 Unix 时间戳
+	if ts, err := strconv.ParseInt(s, 10, 64); err == nil && ts > 1000000000 {
+		return time.Unix(ts, 0)
+	}
+	// 标准格式
+	formats := []string{
+		"Mon Jan  2 15:04:05 2006",
+		"Mon Jan 2 15:04:05 2006",
+		"2006-01-02 15:04:05",
+		time.RFC3339,
+	}
+	for _, f := range formats {
+		if t, err := time.Parse(f, s); err == nil {
+			return t
+		}
+	}
+	return time.Time{}
+}
+
 // cidrToServerDirective 把 "10.8.0.0/24" 转成 OpenVPN server 指令需要的
 // "10.8.0.0 255.255.255.0" 格式(网络地址 + 点分掩码)。
 // 如果输入不含 "/"(已经是 "ip mask" 形式),原样返回。