fix: TUN 子网路由缺失导致客户端无下载流量

- service.go: 移除无意义的 peerIP = serverIP（对端指向自己），改为 nil
- service.go: Configure 之后新增 AddSubnetRoute 调用，确保内核有到 VPN 子网的路由
- tun_linux.go: Configure 增加 peerIP != nil 守卫，nil 时直接走无 peer 分支
- tun_darwin.go: 同上 peerIP != nil 守卫

internal/vpn/service.go

@@ -81,13 +81,15 @@ func (s *VpnService) ApplySettings(settings model.VpnSetting, reservations map[u
 		return err
 	}
 
-	var peerIP net.IP = serverIP
 	if settings.DoLocalIPConfig {
-		if err := tun.Configure(serverIP, prefix, peerIP); err != nil {
+		if err := tun.Configure(serverIP, prefix, nil); err != nil {
 			_ = tun.Close()
 			return fmt.Errorf("配置 TUN 失败: %w", err)
 		}
 	}
+	if err := tun.AddSubnetRoute(ipNet); err != nil {
+		log.Printf("警告: 添加子网路由失败: %v", err)
+	}
 	if err := tun.SetMTU(settings.MTU); err != nil {
 		log.Printf("警告: 设置 MTU 失败: %v", err)
 	}

internal/vpn/tun_darwin.go

@@ -20,13 +20,10 @@ func (t *TUNInterface) Configure(localIP net.IP, prefix int, peerIP net.IP) erro
 	}
 	localCidr := fmt.Sprintf("%s/%d", localIP.String(), prefix)
 	inetType := inetFamily(localIP)
-	var err error
-	if t.Iface.IsTUN() && inetType == "inet" {
-		err = execCmd("ifconfig", t.Name(), inetType, localCidr, peerIP.String(), "up")
-	} else {
-		err = execCmd("ifconfig", t.Name(), inetType, localCidr, "up")
+	if t.Iface.IsTUN() && inetType == "inet" && peerIP != nil {
+		return execCmd("ifconfig", t.Name(), inetType, localCidr, peerIP.String(), "up")
 	}
-	return err
+	return execCmd("ifconfig", t.Name(), inetType, localCidr, "up")
 }
 
 func (t *TUNInterface) AddSubnetRoute(subnet *net.IPNet) error {

internal/vpn/tun_linux.go

@@ -15,13 +15,12 @@ func (t *TUNInterface) Configure(localIP net.IP, prefix int, peerIP net.IP) erro
 		return nil
 	}
 	localCidr := fmt.Sprintf("%s/%d", localIP.String(), prefix)
-	args := []string{"addr", "add", "dev", t.Name(), localCidr, "peer", peerIP.String()}
-	if err := execCmd("ip", args...); err != nil {
-		if err2 := execCmd("ip", "addr", "add", "dev", t.Name(), localCidr); err2 != nil {
-			return err
+	if peerIP != nil {
+		if err := execCmd("ip", "addr", "add", "dev", t.Name(), localCidr, "peer", peerIP.String()); err == nil {
+			return nil
 		}
 	}
-	return nil
+	return execCmd("ip", "addr", "add", "dev", t.Name(), localCidr)
 }
 
 func (t *TUNInterface) AddSubnetRoute(subnet *net.IPNet) error {