feat(tls): manage ACME domain and add desktop client settings

frontend/src/locales/zh-CN.json

@@ -728,6 +728,14 @@
   "protocolIcon": {
     "custom": "自定义协议"
   },
+  "tls": {
+    "title": "域名与证书",
+    "description": "opsx-vpn 可直接监听 80/443，通过 ACME HTTP-01 自动签发和续签；无需 Nginx 或 Certbot。",
+    "domain": "配置域名", "activeDomain": "当前监听域名", "saveDomain": "保存域名", "restartRequired": "域名已保存，重启 opsx-vpn 后才会监听 80/443 并启用自动签发", "saveFailed": "保存域名失败", "dns": "DNS 解析", "certificate": "证书", "valid": "有效", "pending": "等待首次 HTTPS 请求签发",
+    "notConfigured": "未启用", "saved": "域名配置已保存", "issuer": "颁发者", "expires": "到期时间", "renewal": "续签", "automatic": "自动（autocert）",
+    "ports": "监听端口（HTTP / HTTPS）", "setupHint": "保存域名并重启服务，放行公网 TCP 80/443；证书将在该域名首次 HTTPS 访问时签发，缓存于 data/acme。也可用 VPN_TLS_DOMAIN 环境变量设置（优先于页面配置）。请保留数据目录。",
+    "refresh": "刷新状态", "openHttps": "打开 HTTPS 健康检查", "loadFailed": "读取证书状态失败"
+  },
   "protocols": {
     "wireguard": {
       "name": "WireGuard",