perf: fix slow page loads and gate performance in CI

- Ship one hashed Tailwind stylesheet instead of two (one render-blocking)
- Compress responses in-app (brotli/gzip, streaming-safe) and precompress
  the node build so local and CI measurements match production
- Validate the Supabase session once per request
- Render the homepage immediately and stream public stats
- Stream a Pokedex's entries with the page instead of fetching after
  hydration, running the rows and count queries in parallel
- Shrink the avatar and offline placeholder images, fix layout shift,
  contrast, link names and missing meta descriptions
- Add Lighthouse CI (mobile + desktop) with score and metric budgets,
  bundle-size budgets in the build tests, and signed-in speed scenarios

adapter.mjs

@@ -5,9 +5,10 @@ import AdapterNetlify from '@sveltejs/adapter-netlify';
 export const nodeAdapter = process.env.NODE_ADAPTER === 'true';
 
 // Netlify is the deployment target; the node adapter exists so the service worker
-// build tests can check the `build/client` layout a Node server produces.
+// build tests can check the `build/client` layout a Node server produces, and so Lighthouse CI
+// can audit a production build. Netlify's CDN compresses responses, so precompress here to match.
 export const adapter = nodeAdapter
-	? AdapterNode()
+	? AdapterNode({ precompress: true })
 	: AdapterNetlify({
 			// if true, will create a Netlify Edge Function rather
 			// than using standard Node-based functions