fix: auto-install NGINX before Wallarm node setup

Wallarm node (native deployment) requires NGINX as a runtime
dependency.  installNginx() runs apt-get install nginx if not
already present, before extracting/running the Wallarm installer.

Also fixed repo.wallarm.com → meganode.wallarm.com in preflight.

internal/native/native.go

@@ -64,7 +64,10 @@ connector:
 		return fmt.Errorf("write config: %w", err)
 	}
 
-	// 3. Download installer if missing
+	// 3. Ensure NGINX is installed (Wallarm node requires it)
+	installNginx()
+
+	// 4. Download installer if missing
 	url := installerURL()
 	if _, err := os.Stat(installerPath); os.IsNotExist(err) {
 		fmt.Printf("[%s] Downloading installer from meganode.wallarm.com...\n", node.Name)
@@ -233,3 +236,13 @@ WantedBy=multi-user.target
 func CreateNodesDir() error {
 	return os.MkdirAll(NodesDir, 0755)
 }
+
+// installNginx ensures NGINX is present on the system.
+func installNginx() {
+	if _, err := exec.LookPath("nginx"); err == nil {
+		return
+	}
+	fmt.Println("Installing NGINX (required by Wallarm node)...")
+	exec.Command("apt-get", "update", "-qq").Run()
+	exec.Command("apt-get", "install", "-y", "-qq", "nginx").Run()
+}