Bug fix:
- Fix frontend sending captcha_token instead of turnstile_token in
login/register requests (would cause 422 errors on auth)
Backend simplifications:
- Deduplicate VALID_PROVIDERS constant (provider.rs is now the single source)
- Extract validate_display_name/validate_models helpers in provider model
- Add From<UserSettings> for SettingsResponse, From<User> for AdminUserResponse
- Consolidate Resend API call pattern into shared send_via_resend()
- Extract do_bulk_import() for sources bulk/CSV import
- Use idiomatic range.contains() for rate limit validation
Frontend simplifications:
- Consolidate file download logic (exportCsv reuses shared fetchFile/triggerDownload)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
oabrivard