feat(openvpn): suggest available OIDC ports and add deployment assets

frontend/src/locales/en-US.json

@@ -248,7 +248,8 @@
     "baseUrl": "Public sign-in URL",
     "baseTip": "Use a dedicated HTTPS root URL reachable before VPN connection. Give each OIDC tunnel its own endpoint.",
     "listenPort": "Local auth service port",
-    "portTip": "The service listens on 127.0.0.1 only; each tunnel needs a distinct port.",
+    "portTip": "Listens only on 127.0.0.1; no public access needed. New tunnels increment from 19090; +/- and manual entry skip configured and locally occupied ports.",
+    "portLookupFailed": "Could not find an available port. Retry or enter one manually.",
     "callbackTitle": "Register this callback with the final OIDC provider",
     "callbackTip": "With an identity broker, register this URL in the broker's OIDC client, and register the broker's upstream callback in Feishu. Reverse proxy the public endpoint to 127.0.0.1:{port}; :18080 does not handle this callback.",
     "testTip": "Install openvpn-auth-oauth2 and OpenVPN ≥ 2.6.2, then test with a WebAuth-capable client (e.g. OpenVPN Community for Windows or Tunnelblick/Viscosity for macOS). OpenVPN Connect v3 needs individual testing.",

frontend/src/locales/zh-CN.json

@@ -248,7 +248,8 @@
     "baseUrl": "认证入口公网地址",
     "baseTip": "填写独立 HTTPS 域名根地址；客户端未连上 VPN 时也必须能访问。每条 OIDC 专线使用独立入口。",
     "listenPort": "本机认证服务端口",
-    "portTip": "认证服务仅监听 127.0.0.1；多条专线各用不同端口。",
+    "portTip": "仅监听本机 127.0.0.1，无需公网开放。新建专线自动从 19090 起递增；加减或手动输入会跳过已配置和本机正在监听的端口。",
+    "portLookupFailed": "无法获取可用端口，请稍后重试或手动选择",
     "callbackTitle": "在最终 OIDC 身份提供方的客户端中登记此回调地址",
     "callbackTip": "如果通过身份代理接入飞书，本地址登记在代理的 OIDC 客户端中，飞书应用应登记代理的上游回调。将公网入口的所有路径反向代理至本机 127.0.0.1:{port}；不由 :18080 处理。",
     "testTip": "安装 openvpn-auth-oauth2 与 OpenVPN ≥ 2.6.2 后启动专线；使用支持 WebAuth 的客户端试连（如 Windows OpenVPN Community、macOS Tunnelblick/Viscosity）。OpenVPN Connect v3 部分兼容，须实测。",