fix(web): default virtual subnet masks to /24 (#2646)

Co-authored-by: 225284228a-droid <239500008+225284228a-droid@users.noreply.github.com>

easytier-web/frontend-lib/src/locales/cn.yaml

@@ -507,8 +507,8 @@ web:
     virtual_cidr: 虚拟网段
     secure_mode: 安全模式
     secure_mode_hint: 节点间使用 Noise 加密握手与身份认证；开启后可签发临时凭证，设备实例将重建
-    virtual_cidr_hint: 设置后成员将按加入顺序从该网段分配静态 IP（10.x.0.1、.2…）；留空则由节点自动协商（DHCP）
-    virtual_cidr_placeholder: 例如 10.200.0.0/24，留空自动
+    virtual_cidr_hint: 未填写子网掩码时默认补上 /24。设置后成员将按加入顺序从该网段分配静态 IP（10.x.0.1、.2…）；留空则由节点自动协商（DHCP）
+    virtual_cidr_placeholder: 例如 10.200.0.0（默认 /24），留空自动
     peer_urls_placeholder: 每行一个节点地址，例如 tcp://10.0.0.1:11010
     create_hint: 网络密码将自动生成，可在网络详情中查看或重置
     gateway_mode: 接入点

easytier-web/frontend-lib/src/locales/en.yaml

@@ -507,8 +507,8 @@ web:
     virtual_cidr: Virtual Subnet
     secure_mode: Secure Mode
     secure_mode_hint: Noise encrypted handshakes with identity verification; enables temporary credentials. Member instances restart on change
-    virtual_cidr_hint: When set, members get static IPs assigned from this subnet in join order (.1, .2, ...); leave empty for node-negotiated DHCP
-    virtual_cidr_placeholder: e.g. 10.200.0.0/24, empty for auto
+    virtual_cidr_hint: Defaults to /24 when the subnet mask is omitted. When set, members get static IPs assigned from this subnet in join order (.1, .2, ...); leave empty for node-negotiated DHCP
+    virtual_cidr_placeholder: e.g. 10.200.0.0 (defaults to /24), empty for auto
     peer_urls_placeholder: One peer URL per line, e.g. tcp://10.0.0.1:11010
     create_hint: The network secret is generated automatically and can be viewed or reset in the network detail page
     gateway_mode: Gateway