3x-ui agent: 轻量节点 agent 化

- Agent 通过 token 向主控注册，心跳/拉取 xray 配置/上报流量
- 主控按节点下发完整 xray 配置（含出站+路由），agent 只应用不自建
- Agent 心跳同步更新节点在线状态；后台探针跳过 agent 托管节点
- 「添加节点」支持 Agent 类型，自动生成 token 并弹窗展示
- VLESS/SS2022 入站；同机测试支持 api_port 隔离
- 新增 install-master.sh / install-agent.sh 一键安装脚本
- systemd + OpenWrt procd 服务文件，docs/AGENT.md

internal/web/translation/en-US.json

@@ -1179,7 +1179,18 @@
       "pinnedCertPlaceholder": "base64 or hex SHA-256",
       "fetchPin": "Fetch",
       "pinFetched": "Fetched the node's current certificate",
-      "pinFetchFailed": "Could not fetch the certificate"
+      "pinFetchFailed": "Could not fetch the certificate",
+      "nodeType": "Node Type",
+      "nodeTypeTraditional": "Traditional Panel",
+      "nodeTypeAgent": "Agent",
+      "agentHint": "Agent nodes don't need a panel address. An agent token will be generated on creation for configuring the agent on the node machine.",
+      "agentTokenTitle": "Agent Token",
+      "agentTokenCreated": "Node {{name}} created successfully",
+      "agentTokenHint": "Copy the token below and configure it in agent.json on the node machine. This token is shown only once!",
+      "agentTokenInstructions": "Run the install script on the node machine, or manually create /etc/x-ui/agent.json with the master URL and this token, then start the agent.",
+      "agentTokenCopied": "Token copied",
+      "agentTokenCopyFailed": "Copy failed, please copy manually",
+      "copyToken": "Copy Token"
     },
     "settings": {
       "defaultTag": "Default",
@@ -2249,4 +2260,4 @@
     "statusDown": "DOWN",
     "statusUp": "UP"
   }
-}
+}