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/database/model/agent_node.go

@@ -0,0 +1,25 @@
+package model
+
+// AgentNode binds a lightweight agent (token-registered, no web panel) to a
+// 3x-ui node row and carries the per-agent egress configuration.
+//
+// Agents are the only writers of their own LastSeen; the panel owns everything
+// else. Raw tokens are never stored — only the SHA-256 hex of the token.
+type AgentNode struct {
+	Id          int    `json:"id" gorm:"primaryKey;autoIncrement"`
+	TokenHash   string `json:"-" gorm:"size:64;uniqueIndex"`
+	TokenPrefix string `json:"tokenPrefix" gorm:"size:16;index"`
+	Name        string `json:"name"`
+	// NodeID is the 3x-ui node whose inbounds this agent serves. Nil means the
+	// token was issued but not yet bound to a node.
+	NodeID *int `json:"nodeId" gorm:"index"`
+	// Outbounds is the full xray "outbounds" JSON array pushed to this agent,
+	// replacing the template defaults. Empty means "use template defaults".
+	Outbounds string `json:"outbounds" gorm:"type:text"`
+	// RoutingRules is the full xray "routing.rules" JSON array pushed to this
+	// agent, replacing the template defaults. Empty means "use template defaults".
+	RoutingRules string `json:"routingRules" gorm:"type:text"`
+	LastSeen     int64  `json:"lastSeen"`
+	CreatedAt    int64  `json:"createdAt" gorm:"autoCreateTime:milli"`
+	UpdatedAt    int64  `json:"updatedAt" gorm:"autoUpdateTime:milli"`
+}