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

lighthouserc.cjs

@@ -0,0 +1,53 @@
+// Lighthouse CI: `npm run test:lighthouse` builds the Node adapter output, serves it and audits the
+// public pages. Any category below 90 fails the run (and so the PR).
+// Set LHCI_PRESET=desktop to audit with the desktop profile; the default is Lighthouse's mobile
+// profile (slow 4G + CPU throttling), which is the stricter of the two.
+const preset = process.env.LHCI_PRESET === 'desktop' ? 'desktop' : undefined;
+
+module.exports = {
+	ci: {
+		collect: {
+			startServerCommand: 'npm run preview-node',
+			startServerReadyPattern: 'Listening on',
+			url: [
+				'http://localhost:4173/',
+				'http://localhost:4173/signin',
+				'http://localhost:4173/welcome',
+				'http://localhost:4173/offline-guide',
+				'http://localhost:4173/forgot-password'
+			],
+			// Median of three runs smooths out noise from shared CI runners.
+			numberOfRuns: 3,
+			settings: {
+				...(preset ? { preset } : {}),
+				chromeFlags: '--no-sandbox --headless=new'
+			}
+		},
+		assert: {
+			assertions: {
+				'categories:performance': ['error', { minScore: 0.9 }],
+				'categories:accessibility': ['error', { minScore: 0.9 }],
+				'categories:best-practices': ['error', { minScore: 0.9 }],
+				'categories:seo': ['error', { minScore: 0.9 }],
+				// The app compresses its own responses (see src/lib/server/compression.ts and the
+				// precompressed build), so nothing may be served uncompressed.
+				'uses-text-compression': ['error', { minScore: 1 }],
+				// Regression budgets, set a little above what every audited page measured in September
+				// 2026 (mobile profile: LCP 1.4-2.6 s, TBT 0 ms, CLS 0, ~100 KB script, ~14 KB CSS and
+				// ~175 KB in total over the wire). A PR that makes pages meaningfully slower or heavier
+				// fails here even while the category scores stay above 90. When a change legitimately
+				// needs more, raise the number in the same PR so the cost is reviewed.
+				'largest-contentful-paint': ['error', { maxNumericValue: 3000 }],
+				'total-blocking-time': ['error', { maxNumericValue: 200 }],
+				'cumulative-layout-shift': ['error', { maxNumericValue: 0.05 }],
+				'resource-summary:script:size': ['error', { maxNumericValue: 115 * 1024 }],
+				'resource-summary:stylesheet:size': ['error', { maxNumericValue: 20 * 1024 }],
+				'resource-summary:total:size': ['error', { maxNumericValue: 220 * 1024 }]
+			}
+		},
+		upload: {
+			target: 'filesystem',
+			outputDir: '.lighthouseci/reports'
+		}
+	}
+};