[Bug] OAuth login uses international platform URL even when region is set to cn

[DearPeter]

Bug Description

OAuth login URL uses international platform (platform.minimax.io) even when region is configured as 'cn' and base_url is set to domestic Chinese endpoint (api.minimaxi.com). This causes 404 errors for domestic Chinese users.

Environment

• mmx-cli version: 1.0.7
• Region: cn
• Base URL: https://api.minimaxi.com (correct for domestic)
• OS: macOS

Steps to Reproduce

1. Set region to cn: mmx config set --key region --value cn
2. Set base_url to domestic: mmx config set --key base_url --value https://api.minimaxi.com
3. Run mmx auth login
4. Observe the OAuth URL in browser

Actual OAuth URL

https://platform.minimax.io/oauth/authorize?client_id=mmx-cli&response_type=code&redirect_uri=http%3A%2F%2Flocalhost%3A18991%2Fcallback&scope=api&...

Expected OAuth URL

Should use domestic Chinese platform:

https://platform.minimaxi.com/oauth/authorize?...

Result

• Domestic Chinese users get 404 page because their accounts/subscriptions are on platform.minimaxi.com, not platform.minimax.io
• The region setting only affects API base_url but not OAuth URL

Current Workaround

Use API key authentication directly:

mmx config set --key api_key --value YOUR_API_KEY

Suggested Fix

OAuth URL should be derived from region setting or use the same platform domain as base_url:

• For region=cn: use platform.minimaxi.com
• For region=global: use platform.minimax.io

Or add a separate config option for platform_url/auth_url.