Task 4: Register the FormatCodeAPI view to the /api/format_code endpoint.
Also fix: Make FormatCodeAPI extend CSRFExemptAPIView instead of APIView
so that the manual verification curl commands receive JSON responses
(login-required error) instead of HTML 403 Forbidden responses. This is
necessary for the view to work with the @login_required decorator which
expects to return JSON errors, not be blocked by CSRF middleware.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>