perf: optimize Lighthouse scores to 100

Performance:
- Lazy-load ShaderGradientBackground via dynamic import (reduces initial JS ~250KB)
- Disable ShaderGradient animations (animate=off) to reduce CPU/GPU load
- Remove opacity:0 animations from Hero LCP elements for instant paint
- Add browserslist targeting modern browsers (eliminates ~13KB polyfills)

Accessibility:
- Fix color contrast: text-stone-400 → text-stone-600 dark:text-stone-400 on light backgrounds
- Fix text-liquid-mint → text-emerald-700/600 for readable text/accent dots
- Fix quote text contrast on dark status box (text-stone-700 → text-stone-300)
- Fix Online badge contrast (emerald-600 → emerald-700)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

package.json

@@ -86,6 +86,12 @@
     "tailwind-merge": "^2.6.0",
     "three": "^0.183.1"
   },
+  "browserslist": [
+    "last 2 Chrome versions",
+    "last 2 Firefox versions",
+    "last 2 Safari versions",
+    "last 2 Edge versions"
+  ],
   "devDependencies": {
     "@eslint/eslintrc": "^3",
     "@playwright/test": "^1.57.0",