Conform blueprint launches to desired fleet counts

src/routes/api/deployments/preview/+server.ts

@@ -5,6 +5,7 @@ export async function POST({ request }: { request: Request }) {
     try {
         const body = await request.json();
         if (!body || typeof body !== 'object' || Array.isArray(body)) throw new Error('Provide a launch selection.');
+        if (body.blueprintId !== undefined) throw new Error('Blueprints use target counts. Use /api/deployment-collections/preview to preview only missing servers.');
         return json(previewCreation(body));
     } catch (err) {
         return json({ error: (err as Error).message }, { status: 400 });