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/store/store.go

@@ -44,7 +44,7 @@ func Init(dataDir string) error {
 	}
 	// 兼容旧库：VPNUser 唯一约束曾是 username 单列全局唯一
 	db.Exec("DROP INDEX IF EXISTS idx_vpn_user")
-	if err := db.AutoMigrate(&model.User{}, &model.LDAPConfig{}, &model.MFADevice{}, &model.VPNUser{}, &model.Tunnel{}, &model.Node{}, &model.Plugin{}, &model.AuditLog{}, &model.VPNSession{}, &model.ConnectionLog{}, &model.TrafficPolicy{}); err != nil {
+	if err := db.AutoMigrate(&model.User{}, &model.LDAPConfig{}, &model.MFADevice{}, &model.VPNUser{}, &model.Tunnel{}, &model.Node{}, &model.Plugin{}, &model.AuditLog{}, &model.VPNSession{}, &model.ConnectionLog{}, &model.TrafficPolicy{}, &model.TrafficSample{}); err != nil {
 		return err
 	}
 	DB = db