1. console.cloud.google.com → create a new project.
2. APIs & Services → Library → enable Google Calendar API.
3. OAuth consent screen → External → fill in name + your email → add yourself as a test user.
4. Credentials → Create Credentials → OAuth client ID → Web application.
5. Authorized JavaScript origins: paste your Cloudflare URL (e.g. https://family-hub.pages.dev) with no trailing slash.
6. Copy the Client ID and paste it above.