build: carry the heap ceiling in the build script itself

`next build` needs more than Node's 4 GB default: the TypeScript pass after
compilation runs the whole project through the checker and dies with
"Ineffective mark-compacts near heap limit" at around 4.07 GB.

CI and the production image already knew that. `e2e.yml` and the Dockerfile both
invoke the build with `--max-old-space-size=8192`. The bare `pnpm build` did not,
so the one place that ran with the default was a local gate — which then failed
for a condition that exists in neither environment that matters, and would have
kept failing every time somebody ran the documented gate.

Three places declared how the build is invoked and one of them disagreed. The
script now carries it, so a local run, CI and the image all get the same ceiling.
The existing prefixes in the workflow and the Dockerfile stay: they are harmless
now, and removing them would put the knowledge back in more than one place.

package.json

@@ -28,7 +28,7 @@
     "dev": "next dev",
     "predev": "node scripts/generate-i18n-boot.mjs",
     "prebuild": "node scripts/generate-sw-version.mjs && node scripts/generate-i18n-boot.mjs",
-    "build": "next build",
+    "build": "NODE_OPTIONS=--max-old-space-size=8192 next build",
     "analyze": "ANALYZE=1 next build",
     "bundle-report": "node scripts/check-bundle-budget.mjs",
     "bundle-check": "node scripts/check-bundle-budget.mjs --check",