feat(vpn): VPN on-demand Tailscale + agent studioE5 standalone

- Agent studioE5 standalone en Go (console + systray)
- VPN on-demand via tailscaled + tailscale up (authkey Headscale)
- Resolver/serveur dans le tailnet studioe5
- Caddy on-demand TLS pour les instances
- Nouveaux endpoints serveur /api/internal/send-to-node
- Suppression des anciens binaires edubox-agent
- Suivi dans SUIVI_VPN_ONDEMAND.md

agent/systray.go

@@ -0,0 +1,90 @@
+package main
+
+import (
+	_ "embed"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"runtime"
+	"strings"
+	"time"
+
+	"fyne.io/systray"
+)
+
+//go:embed icon.png
+var iconBytes []byte
+
+const uiURL = "http://localhost:7070"
+
+func runTray(appName string, shutdownCh chan struct{}) {
+	systray.Run(func() { onTrayReady(appName, shutdownCh) }, func() { onTrayExit(shutdownCh) })
+}
+
+func onTrayReady(appName string, shutdownCh chan struct{}) {
+	systray.SetIcon(iconBytes)
+	systray.SetTitle(appName)
+	systray.SetTooltip(fmt.Sprintf("%s Agent - Cliquez pour ouvrir l'interface", appName))
+
+	mOpen := systray.AddMenuItem("Ouvrir l'interface", "Ouvrir l'interface web locale")
+	mInstances := systray.AddMenuItem("Mes instances", "Afficher les instances")
+	mSettings := systray.AddMenuItem("Paramètres", "Ouvrir les paramètres")
+	systray.AddSeparator()
+	mQuit := systray.AddMenuItem("Quitter", "Arrêter l'agent")
+
+	go func() {
+		for {
+			select {
+			case <-mOpen.ClickedCh:
+				openBrowser(uiURL)
+			case <-mInstances.ClickedCh:
+				openBrowser(uiURL + "#instances")
+			case <-mSettings.ClickedCh:
+				openBrowser(uiURL + "#settings")
+			case <-mQuit.ClickedCh:
+				close(shutdownCh)
+				systray.Quit()
+				return
+			}
+		}
+	}()
+}
+
+func onTrayExit(shutdownCh chan struct{}) {
+	log.Printf("Tray exit requested")
+	// If the user did not already trigger shutdown via the menu, signal it now.
+	select {
+	case <-shutdownCh:
+	default:
+		close(shutdownCh)
+	}
+	// Give other goroutines a moment to clean up, then exit.
+	time.Sleep(200 * time.Millisecond)
+	os.Exit(0)
+}
+
+func openBrowser(url string) {
+	var cmd string
+	var args []string
+
+	switch runtime.GOOS {
+	case "windows":
+		cmd = "rundll32"
+		args = []string{"url.dll,FileProtocolHandler", url}
+	case "darwin":
+		cmd = "open"
+		args = []string{url}
+	default:
+		cmd = "xdg-open"
+		args = []string{url}
+	}
+
+	if err := exec.Command(cmd, args...).Start(); err != nil {
+		log.Printf("Failed to open browser: %v", err)
+	}
+}
+
+func normalizeName(name string) string {
+	return strings.ReplaceAll(name, " ", "")
+}