perf: cut CI time, fix CSS chain, fix iPad hero layout, fix contrast

CI:
- Replace `npm run build` with `tsc --noEmit` in test-build job
  → eliminates duplicate Next.js build (~5 min saved per push)
  → Docker deploy job already does the full build

PageSpeed:
- Add `cssChunking: 'loose'` to merge CSS into one chunk and break
  the 84dc7384→3aefc04b render-blocking CSS waterfall chain (450ms mobile)
- Remove @shadergradient/react, @react-three/fiber, three from
  package.json — packages were already unused in code, removes any
  residual bundling risk for chunk 7001

Hero:
- Change lg:flex-row → xl:flex-row so iPad (1024px) stays in column
  layout; the 9.5rem heading overflowed into the image at lg causing
  the photo to be clipped by overflow-hidden on the section
- Update image sizes attribute to match new xl breakpoint
- Fix contrast: "GET IN TOUCH" link text-stone-500 → text-stone-700
  (contrast 3.7:1 → 7:1, now WCAG AA compliant)
- Change text-center/justify-center to xl: variants to match layout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -54,8 +54,6 @@
   "dependencies": {
     "@next/bundle-analyzer": "^15.1.7",
     "@prisma/client": "^5.22.0",
-    "@react-three/fiber": "^9.5.0",
-    "@shadergradient/react": "^2.4.20",
     "@swc/helpers": "^0.5.19",
     "@tiptap/extension-color": "^3.15.3",
     "@tiptap/extension-highlight": "^3.15.3",
@@ -82,8 +80,7 @@
     "react-markdown": "^10.1.0",
     "redis": "^5.8.2",
     "sanitize-html": "^2.17.0",
-    "tailwind-merge": "^2.6.0",
-    "three": "^0.183.1"
+    "tailwind-merge": "^2.6.0"
   },
   "browserslist": [
     "chrome >= 100",