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/ui.go

@@ -2,9 +2,12 @@ package main
 
 import (
 	_ "embed"
+	"encoding/json"
 	"fmt"
 	"log"
 	"net/http"
+	"os"
+	"os/exec"
 
 	"github.com/gorilla/websocket"
 )
@@ -20,6 +23,55 @@ func startUI(dataDir, nodeID, serverAddr string) {
 		fmt.Fprint(w, uiHTML)
 	})
 
+	http.HandleFunc("/api/config", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		switch r.Method {
+		case http.MethodGet:
+			cfg, _, err := loadOrCreateConfig(dataDir)
+			if err != nil {
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+				return
+			}
+			// Do not expose the auth key in plain GET unless requested; for local UI it is fine.
+			json.NewEncoder(w).Encode(cfg)
+		case http.MethodPost:
+			var cfg AgentConfig
+			if err := json.NewDecoder(r.Body).Decode(&cfg); err != nil {
+				http.Error(w, err.Error(), http.StatusBadRequest)
+				return
+			}
+			if cfg.DataDir == "" {
+				cfg.DataDir = dataDir
+			}
+			if err := saveConfig(dataDir, &cfg); err != nil {
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+				return
+			}
+			w.WriteHeader(http.StatusNoContent)
+		default:
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		}
+	})
+
+	http.HandleFunc("/api/restart", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+		w.WriteHeader(http.StatusNoContent)
+		go func() {
+			cmd := exec.Command(os.Args[0], os.Args[1:]...)
+			cmd.Stdout = os.Stdout
+			cmd.Stderr = os.Stderr
+			cmd.Stdin = os.Stdin
+			if err := cmd.Start(); err != nil {
+				log.Printf("Restart failed: %v", err)
+				return
+			}
+			os.Exit(0)
+		}()
+	})
+
 	http.HandleFunc("/ws", func(w http.ResponseWriter, r *http.Request) {
 		conn, err := upgrader.Upgrade(w, r, nil)
 		if err != nil {
@@ -72,9 +124,9 @@ func startUI(dataDir, nodeID, serverAddr string) {
 	})
 
 	port := "7070"
-	log.Printf("UI starting on http://localhost:%s", port)
+	log.Printf("%s UI starting on http://localhost:%s", APP_NAME, port)
 	if err := http.ListenAndServe("127.0.0.1:"+port, nil); err != nil {
-		log.Fatalf("UI server error: %v", err)
+		log.Fatalf("%s UI server error: %v", APP_NAME, err)
 	}
 }