Feedback portal: compressed assets, lazy our auth provider, SWR on public routes

Mirror pass to the admin perf work, but for the feedback portal — and with one extra: SWR caching on the public read-only routes (boards, stages, posts) so subsequent visitors hit a warm cache while a background refresh keeps it current.

Plus the same hits: assets compressed, trackers deferred, auth SDK lazy. Lighthouse scores on the portal are now consistently above 90 across performance, accessibility, best practices, and SEO.