Design the admin panel to control the authentication and default keys

Implement a UI using next.js to support admin activities:

- Enable or disable the API authentication.
- Add default keys for the AI model providers.
- The admin page protected by password in the `.env` file.

Start by locating the Next.js admin-page entry point and reviewing how the password in `.env` is currently handled. Define the page's completion criteria around toggling API authentication, configuring default AI-provider keys, and requiring the configured admin password.

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