you can register any accout by post /auth/login/sentry

### Environment SaaS (https://sentry.io/) ### Steps to Reproduce <img width="726" height="271" alt="Image" src="https://github.com/user-attachments/assets/f332d5e2-d235-4d81-b828-b8cebbfcf66f" /> If you change `op=login` to `op=register`, you can register any account. ### Expected Result fix it ### Actual Result you can register any accout by post /auth/login/sentry ### Product Area Unknown ### Link _No response_ ### DSN _No response_ ### Version _No response_