Deploy to Vercel button doesn't work

1. Go to https://github.com/keystonejs/keystone/tree/main/examples/framework-nextjs-app-directory
2. Click the `Deploy` button at the end of the README.md
3. Choose a new private repo, and then get an error:
```
[20:07:19.021] Running build in Washington, D.C., USA (East) – iad1
[20:07:19.021] Build machine configuration: 2 cores, 8 GB
[20:07:19.044] Cloning github.com/pahaz/test-keystone-deploy-to-versel (Branch: main, Commit: 30a8094)
[20:07:19.223] Previous build caches not available
[20:07:19.537] Cloning completed: 492.000ms
[20:07:19.840] Running "vercel build"
[20:07:20.277] Vercel CLI 43.3.0
[20:07:20.565] Installing dependencies...
[20:07:21.872] npm error code ERESOLVE
[20:07:21.873] npm error ERESOLVE unable to resolve dependency tree
[20:07:21.873] npm error
[20:07:21.874] npm error While resolving: @keystone-6/example-framework-nextjs-app-directory@null
[20:07:21.874] npm error Found: react@19.1.0
[20:07:21.874] npm error node_modules/react
[20:07:21.874] npm error dev react@"^19.0.0" from the root project
[20:07:21.875] npm error
[20:07:21.875] npm error Could not resolve dependency:
[20:07:21.876] npm error peer react@"^18.3.1" from @keystone-6/auth@8.1.0
[20:07:21.876] npm error node_modules/@keystone-6/auth
[20:07:21.876] npm error @keystone-6/auth@"^8.1.0" from the root project
[20:07:21.876] npm error
[20:07:21.877] npm error Fix the upstream dependency conflict, or retry
[20:07:21.877] npm error this command with --force or --legacy-peer-deps
[20:07:21.877] npm error to accept an incorrect (and potentially broken) dependency resolution.
[20:07:21.878] npm error
[20:07:21.878] npm error
[20:07:21.878] npm error For a full report see:
[20:07:21.878] npm error /vercel/.npm/_logs/2025-06-23T17_07_20_781Z-eresolve-report.txt
[20:07:21.879] npm error A complete log of this run can be found in: /vercel/.npm/_logs/2025-06-23T17_07_20_781Z-debug-0.log
[20:07:21.908] Error: Command "npm install" exited with 1
[20:07:22.137]
[20:07:25.034] Exiting build container
```

Start with examples/framework-nextjs-app-directory/README.md and the example's dependency manifest. Reproduce the README Deploy button flow on Vercel and inspect the React peer-dependency conflict between the example and @keystone-6/auth. Done means the generated repository installs dependencies and completes its Vercel build successfully.

Written by the indexing model from the issue text.