The sx-handle-request function (which routes URLs to page rendering)
was removed from request-handler.sx. Without it, the server's
http_render_page calls sx-handle-request which doesn't exist,
returning nil for every request → 500 errors.
Restored from the last known working version (394c86b).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>