The signup function was not reading the response body before throwing
an error, causing users to see only "400 Bad Request" instead of the
actual validation message.
Changes:
- Read response body in signup() to capture error details
- Add 400 status handling in Login.vue to display errors in form
- Parse password length errors to show user-friendly message
- Add translation string for password minimum length error
Fixes#5499🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
7bae594138