fix: agent install.sh 404 + 三阶段构建编译agent二进制

问题: 构建上下文 ./backend 无法访问 ../agent, 导致容器内
/app/agent/deploy/install.sh 不存在, 返回 404

修复:
- Dockerfile 改为三阶段构建 (backend go1.21 + agent go1.24 交叉编译 + alpine runtime)
- docker-compose backend build context 改为项目根
- routes.go /agent/arch 安装命令改为动态获取 URL
- 新增 .dockerignore
- agent_install.go: SSH 远程安装 handler
- AgentWizard.tsx: 复制按钮 fallback + 动态 server URL
- ServerTableRow.tsx: agent 状态判断

验证: curl|bash 安装成功, agent 上报数据到 MySQL ✅

backend/internal/api/handlers/agent_install.go

@@ -0,0 +1,146 @@
+package handlers
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"strconv"
+	"time"
+
+	"ezops/internal/models"
+
+	"github.com/gin-gonic/gin"
+	"golang.org/x/crypto/ssh"
+	"gorm.io/gorm"
+)
+
+// AgentInstallHandler Agent 远程安装处理器 // Logan.Li
+type AgentInstallHandler struct {
+	db *gorm.DB
+}
+
+func NewAgentInstallHandler(db *gorm.DB) *AgentInstallHandler {
+	return &AgentInstallHandler{db: db}
+}
+
+// sshDial 复用 webshell.go 的 SSH 连接逻辑
+func sshDial(server models.Server) (*ssh.Client, error) {
+	config := &ssh.ClientConfig{
+		User:            server.Username,
+		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
+		Timeout:         10 * time.Second,
+	}
+
+	switch server.AuthType {
+	case "key":
+		signer, err := ssh.ParsePrivateKey([]byte(server.SSHKey))
+		if err != nil {
+			config.Auth = []ssh.AuthMethod{ssh.Password(server.Password)}
+		} else {
+			config.Auth = []ssh.AuthMethod{ssh.PublicKeys(signer)}
+		}
+	default:
+		config.Auth = []ssh.AuthMethod{ssh.Password(server.Password)}
+	}
+
+	addr := server.IP + ":" + strconv.Itoa(server.Port)
+	return ssh.Dial("tcp", addr, config)
+}
+
+// runSSHCommand 在远程主机执行命令并返回输出
+func runSSHCommand(client *ssh.Client, cmd string) (string, error) {
+	session, err := client.NewSession()
+	if err != nil {
+		return "", err
+	}
+	defer session.Close()
+
+	output, err := session.CombinedOutput(cmd)
+	return string(output), err
+}
+
+// InstallAgent 远程安装 Agent 到指定服务器
+// POST /servers/:id/install-agent
+func (h *AgentInstallHandler) InstallAgent(c *gin.Context) {
+	id, _ := strconv.Atoi(c.Param("id"))
+
+	var server models.Server
+	if err := h.db.First(&server, id).Error; err != nil {
+		c.JSON(http.StatusNotFound, models.Response{Code: 404, Message: "服务器不存在"})
+		return
+	}
+
+	if server.Status != "running" {
+		c.JSON(http.StatusBadRequest, models.Response{Code: 400, Message: "服务器未运行，无法安装 Agent"})
+		return
+	}
+
+	// 1. SSH 连接目标主机
+	client, err := sshDial(server)
+	if err != nil {
+		log.Printf("[AgentInstall] SSH连接失败 %s: %v", server.IP, err)
+		c.JSON(http.StatusOK, models.Response{
+			Code:    500,
+			Message: "SSH 连接失败: " + formatSSHError(err),
+		})
+		return
+	}
+	defer client.Close()
+
+	// 2. 检测系统架构
+	archOut, _ := runSSHCommand(client, "uname -m")
+	arch := "amd64"
+	if len(archOut) > 0 && (contains(archOut, "aarch64") || contains(archOut, "arm64")) {
+		arch = "arm64"
+	}
+
+	// 3. 构造安装命令（使用 Agent API 服务地址）
+	// 从请求头获取后端可访问地址
+	serverURL := fmt.Sprintf("http://%s", c.Request.Host)
+	token := c.Query("token")
+
+	installCmd := fmt.Sprintf(
+		`curl -fsSL %s/agent/install.sh | sudo bash -s -- --server %s --token %s`,
+		serverURL, serverURL, token,
+	)
+
+	// 4. 执行安装
+	installOut, err := runSSHCommand(client, installCmd)
+	if err != nil {
+		c.JSON(http.StatusOK, models.Response{
+			Code:    500,
+			Message: "安装命令执行失败（可能需要 sudo 权限或 curl 未安装）",
+			Data:    installOut,
+		})
+		return
+	}
+
+	// 5. 验证安装是否成功
+	verifyOut, _ := runSSHCommand(client, "systemctl is-active aiops-agent 2>/dev/null || echo 'not_found'")
+	installed := contains(verifyOut, "active") || contains(verifyOut, "running")
+
+	if installed {
+		// 更新服务器 Agent 状态
+		h.db.Model(&server).Updates(map[string]interface{}{
+			"agent_status":  "online",
+			"agent_version": "installed",
+			"last_check_at": time.Now(),
+		})
+	}
+
+	c.JSON(http.StatusOK, models.Response{
+		Code:    200,
+		Message: func() string {
+			if installed {
+				return "Agent 安装成功，已自动启动并设置开机自启"
+			}
+			return "安装命令已执行，但 Agent 服务未检测到运行（请查看日志排查）"
+		}(),
+		Data: gin.H{
+			"installed": installed,
+			"arch":      arch,
+			"output":    installOut,
+			"verify":    verifyOut,
+		},
+	})
+}