lith: drop redundant Link preload header for boot.mjs + style.css
Was triggering credentials-mode mismatch (as=script vs module CORS) and
"preloaded but not used" warnings (service worker intercepts the fetch).
HTML modulepreload hints + sw.js precache cover the same job.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>