add shared computer feature

frontend/src/routes/api/device/remove/+server.ts

@@ -0,0 +1,23 @@
+import { json, error } from '@sveltejs/kit';
+import type { RequestEvent } from '@sveltejs/kit';
+import {
+	ACTIVE_COOKIE,
+	childSessionCookie,
+	clearChildSession,
+	clearActiveChild
+} from '$lib/server/session';
+
+// Remove ONE child profile from this device (picker ✕). Device-local cookie
+// surgery only — no PB writes, no session required (the picker is reachable
+// with no active user).
+export async function POST(event: RequestEvent) {
+	const body = await event.request.json().catch(() => ({}));
+	const { userId } = body as { userId?: string };
+	if (!userId) throw error(400, 'Missing userId');
+	if (!event.cookies.get(childSessionCookie(userId))) {
+		throw error(400, 'No session on this device');
+	}
+	clearChildSession(event.cookies, userId);
+	if (event.cookies.get(ACTIVE_COOKIE) === userId) clearActiveChild(event.cookies);
+	return json({ ok: true });
+}