feat: 日志中心 + GRE协议支持 + 流量监控 + 部署脚本

- 新增日志中心功能 (api/logapi.go + Logs.vue)
- 新增GRE协议服务支持 (service/gre/)
- 新增流量监控组件 (TrafficChart.vue)
- 新增L2TP/IPSec测试用例
- 新增日志轮转服务 (logrotate.go)
- 新增部署脚本 (scripts/install.sh, uninstall.sh, service文件)
- 更新i18n国际化文件
- 优化后端API和前端路由

backend/internal/service/l2tp/l2tp.go

@@ -90,6 +90,11 @@ func parseIPRange(raw string) (netip.Addr, netip.Addr, error) {
 }
 
 func (s *Service) Create(t *model.Tunnel) error {
+	// Ensure strongSwan certificate directories exist (required by swanctl --load-all)
+	dir := service.InstanceDir(t)
+	for _, sub := range []string{"x509", "x509ca", "x509ocsp", "x509aa", "x509ac", "x509crl", "pubkey", "private", "rsa", "ecdsa", "pkcs8", "pkcs12"} {
+		_ = os.MkdirAll(dir+"/"+sub, 0700)
+	}
 	cfg, err := store.TunnelConfig(t)
 	if err != nil {
 		return err
@@ -116,12 +121,12 @@ func (s *Service) Create(t *model.Tunnel) error {
 	// 1) IPSec 层（transport 模式，L2TP over IPSec）
 	swanConf := fmt.Sprintf(`connections {
     l2tp-%d {
-        type = transport
         proposals = %s
         local { auth = psk }
         remote { auth = psk }
         children {
             l2tp-child-%d {
+                mode = transport
                 local_ts = dynamic[udp/l2tp]
                 remote_ts = dynamic[udp/l2tp]
                 esp_proposals = %s