Registration Form shows "error.[object Object]" on Errors

**Describe the bug** When attempting to register an account against Lemmy 0.19.13, the following form errors display "error.[object Object]" instead of a useful error message: - Invalid username (contained hyphens) - Email already registered - Rate limiting **To Reproduce** (if applicable) Steps to reproduce the behavior: 1. Navigate to the registration page 2. Plug in values that would result in an error 3. Click "Submit" 4. Observe error **Expected behavior** The error message should show the contents of the error returned by Lemmy. **Screenshots** (In this one, the issue is that the email's already in use, but it's not any different from other issue cases listed above) <img width="717" height="499" alt="Image" src="https://github.com/user-attachments/assets/52ce24ce-feee-4b26-9e2a-37f01f835384" /> **Versions** - Browser: Firefox - Photon version: 2.2.0 - Lemmy version: 0.19.13