Replace the text brand in the header and footer with the logo the source site
publishes for its footer (637x220 PNG, BRAND.logoSourceUrl):
- src/store/constants.ts: add BRAND (source URL, local path, dimensions).
- scripts/fetch-logo.ts: mirror it into public/images/brand/logo_footer.png
(idempotent, --force to refresh); `pnpm fetch:logo` runs it standalone.
- scripts/dev-server.ts: ensure the logo at boot, non-fatal on failure.
- public/index.html: <img class="brand__logo"> in the header (the wordmark is
dark on the light header) and <img class="footer__logo"> in the footer, on a
white plate because the footer is dark.
- public/styles.css: logo sizing (30px / 40px from 768px) + the footer plate.
