💥 feat(agent)!: 添加主机监控代理首版

* 实现周期采集、快照缓存、本地 HTTP API 和主动上报

* 补齐 Linux 和 Windows 主机、网络、资源、进程和 TCP 采集

* 添加服务生命周期管理、配置加载、构建脚本和测试覆盖

BREAKING CHANGE: network.ips 拆分为 network.ipv4s 和 network.ipv6s。

internal/service/service_linux.go

@@ -0,0 +1,82 @@
+//go:build linux
+
+package service
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+
+	"mfd-monitor-agent/internal/config"
+)
+
+var currentUID = os.Geteuid
+
+// linuxManager manages a systemd service for the agent.
+type linuxManager struct{}
+
+// newManager returns the Linux systemd-backed service manager.
+func newManager() Manager {
+	return linuxManager{}
+}
+
+// Install writes a systemd unit, reloads systemd, and enables the configured service.
+func (linuxManager) Install(executable string, cfg config.Config, opts InstallOptions) error {
+	if currentUID() != 0 {
+		return fmt.Errorf("install requires root")
+	}
+	unit := renderSystemdUnit(executable, opts.ConfigPath, cfg)
+	path := "/etc/systemd/system/" + cfg.Service.Name + ".service"
+	if err := os.WriteFile(path, []byte(unit), 0644); err != nil {
+		return fmt.Errorf("write systemd unit: %w", err)
+	}
+	if err := exec.Command("systemctl", "daemon-reload").Run(); err != nil {
+		return fmt.Errorf("systemctl daemon-reload: %w", err)
+	}
+	if err := exec.Command("systemctl", "enable", cfg.Service.Name).Run(); err != nil {
+		return fmt.Errorf("systemctl enable: %w", err)
+	}
+	return nil
+}
+
+// renderSystemdUnit builds the Linux systemd unit used by Install.
+func renderSystemdUnit(executable string, configPath string, cfg config.Config) string {
+	args := []string{executable, "run"}
+	if configPath != "" {
+		args = append(args, "-config", configPath)
+	}
+	return fmt.Sprintf(`[Unit]
+Description=%s
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=%s
+Restart=always
+RestartSec=5s
+
+[Install]
+WantedBy=multi-user.target
+`, cfg.Service.Description, strings.Join(args, " "))
+}
+
+// Uninstall disables the service, removes its unit file, and reloads systemd.
+func (linuxManager) Uninstall(cfg config.Config) error {
+	_ = exec.Command("systemctl", "disable", "--now", cfg.Service.Name).Run()
+	if err := os.Remove("/etc/systemd/system/" + cfg.Service.Name + ".service"); err != nil && !os.IsNotExist(err) {
+		return err
+	}
+	return exec.Command("systemctl", "daemon-reload").Run()
+}
+
+// Start asks systemd to start the configured service.
+func (linuxManager) Start(cfg config.Config) error {
+	return exec.Command("systemctl", "start", cfg.Service.Name).Run()
+}
+
+// Stop asks systemd to stop the configured service.
+func (linuxManager) Stop(cfg config.Config) error {
+	return exec.Command("systemctl", "stop", cfg.Service.Name).Run()
+}