feat(agent): v0.3.5 Windows inbound forwarding, UI actions, lifecycle

- Configure tailscale serve automatically for each instance on Windows userspace networking.
- Add local UI buttons: start/stop/reset/delete instances (stop/start preserve volumes).
- Clean shutdown: stop tailscaled and instances, notify server with instance_stopped.
- Restart tailscaled on agent boot using persisted state when pre-auth key is absent.
- Sync instance stopped/deleted status to dashboard (server/lib/websocket.ts).
- Security: include prior authz/scoping changes across API routes, ephemeral pre-auth keys, ACL policy, internal API key.
- Update SUIVI_VPN_ONDEMAND.md and docs/ONBOARDING_CLIENT.md.
- Bump agent version to 0.3.5.

server/lib/api-auth.ts

@@ -0,0 +1,39 @@
+import { NextResponse } from "next/server";
+import { getServerSession } from "next-auth/next";
+import { authOptions } from "./auth-config";
+
+export type ApiUser = {
+  id: string;
+  email: string;
+  role: "superadmin" | "admin" | "teacher";
+  establishmentId?: string;
+};
+
+export async function requireAuth(): Promise<ApiUser | NextResponse> {
+  const session = await getServerSession(authOptions);
+  if (!session?.user) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+  return session.user as ApiUser;
+}
+
+export function requireRole(user: ApiUser, ...allowed: string[]): NextResponse | null {
+  if (!allowed.includes(user.role)) {
+    return NextResponse.json({ error: "Forbidden" }, { status: 403 });
+  }
+  return null;
+}
+
+export function forbidden(): NextResponse {
+  return NextResponse.json({ error: "Forbidden" }, { status: 403 });
+}
+
+export function getScopedEstablishmentId(user: ApiUser, requested?: string | null): string | undefined | NextResponse {
+  if (user.role === "superadmin") {
+    return requested ?? undefined;
+  }
+  if (requested && requested !== user.establishmentId) {
+    return forbidden();
+  }
+  return user.establishmentId;
+}