fix: activation via connexion WS principale, cascade delete student→nodes, lien fiche étudiant

- agent/websocket.go: expose sendMessage() + notifyUI() pour broadcaster
  les résultats d'activation à tous les clients UI connectés
- agent/ui.go: supprime forwardActivation(), utilise sendMessage() sur
  la connexion WS principale au lieu d'une connexion temporaire
- agent/activation.go: ajoute os.MkdirAll avant l'écriture d'activation.json
- server/prisma/schema.prisma: onDelete Cascade sur Node→Student
- server/app/dashboard/students/page.tsx: nom cliquable vers fiche détail
- server/app/dashboard/students/[id]/actions.ts: deleteMany → delete

server/app/dashboard/students/[id]/actions.ts

@@ -23,12 +23,15 @@ export async function deleteStudent(formData: FormData) {
   if (!id) return;
 
   const establishmentId = session.user.establishmentId;
-  await prisma.student.deleteMany({
+  const student = await prisma.student.findFirst({
     where: {
       id,
       class: establishmentId ? { establishmentId } : undefined,
     },
   });
+  if (!student) return;
+
+  await prisma.student.delete({ where: { id } });
 
   redirect("/dashboard/students");
 }

server/app/dashboard/students/page.tsx

@@ -47,7 +47,11 @@ export default async function StudentsPage() {
                 const node = s.nodes[0];
                 return (
                   <TableRow key={s.id}>
-                    <TableCell className="font-medium">{s.firstName} {s.lastName}</TableCell>
+                    <TableCell className="font-medium">
+                      <Link href={`/dashboard/students/${s.id}`} className="hover:underline">
+                        {s.firstName} {s.lastName}
+                      </Link>
+                    </TableCell>
                     <TableCell>{s.class.name}</TableCell>
                     <TableCell>{s.email}</TableCell>
                     <TableCell>{s.activationCode || "-"}</TableCell>

server/lib/websocket.ts

@@ -18,10 +18,12 @@ const nodes = new Map<string, WebSocket>();
 export function initWebSocketServer(wss: WebSocketServer) {
   wss.on("connection", (ws: WebSocket) => {
     let nodeId: string | null = null;
+    console.log("[WS] New connection");
 
     ws.on("message", async (raw) => {
       try {
         const msg: NodeMessage = JSON.parse(raw.toString());
+        console.log("[WS] Received:", msg.action, "from", msg.nodeId || nodeId);
 
         if (msg.action === "register" && msg.nodeId) {
           nodeId = msg.nodeId;
@@ -41,6 +43,7 @@ export function initWebSocketServer(wss: WebSocketServer) {
             where: { activationCode: msg.code },
           });
           if (!student) {
+            console.log("[WS] Invalid code:", msg.code);
             ws.send(JSON.stringify({ action: "activation_failed", error: "Invalid code" }));
             return;
           }
@@ -49,6 +52,7 @@ export function initWebSocketServer(wss: WebSocketServer) {
             update: { studentId: student.id, status: "online", lastSeen: new Date() },
             create: { id: nodeId, studentId: student.id, status: "online", lastSeen: new Date() },
           });
+          console.log("[WS] Activated:", student.firstName, student.lastName, "on", nodeId);
           ws.send(JSON.stringify({ action: "activated", studentId: student.id, studentName: `${student.firstName} ${student.lastName}` }));
           return;
         }
@@ -83,6 +87,7 @@ export function initWebSocketServer(wss: WebSocketServer) {
     });
 
     ws.on("close", async () => {
+      console.log("[WS] Connection closed for", nodeId);
       if (nodeId) {
         nodes.delete(nodeId);
         await prisma.node.upsert({

server/prisma/schema.prisma

@@ -63,7 +63,7 @@ model Student {
 model Node {
   id          String     @id
   studentId   String?
-  student     Student?   @relation(fields: [studentId], references: [id], onDelete: SetNull)
+  student     Student?   @relation(fields: [studentId], references: [id], onDelete: Cascade)
   tailscaleIp String?
   status      String     @default("offline")
   lastSeen    DateTime?