fix: raise eleventy heap cap from 2048 to 3072 MB

#397 lowered --max-old-space-size from 4096 to 2048 based on a 210-page
garden. Large text-heavy gardens (~1100+ notes) exceed that: the build
dies with a V8 "allocation failure" at ~2 GB heap while the 4Gi build
container still has half its memory unused.

3072 gives those gardens room while still leaving ~1 GB on a 4Gi
container for sharp's native allocations, which was the reason #397
lowered it in the first place.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FuHUwv79QekUJwCMB4rpvh

Author: oleeskild

package.json

@@ -8,7 +8,7 @@
         "dev": "npm-run-all get-theme build:sass --parallel watch:*",
         "watch:sass": "sass --watch src/site/styles:dist/styles",
         "watch:eleventy": "cross-env ELEVENTY_ENV=dev eleventy --serve",
-        "build:eleventy": "cross-env ELEVENTY_ENV=prod UV_THREADPOOL_SIZE=16 NODE_OPTIONS=--max-old-space-size=2048 eleventy",
+        "build:eleventy": "cross-env ELEVENTY_ENV=prod UV_THREADPOOL_SIZE=16 NODE_OPTIONS=--max-old-space-size=3072 eleventy",
         "build:sass": "sass src/site/styles:dist/styles --style compressed",
         "get-theme": "node src/site/get-theme.js",
         "build": "npm-run-all get-theme build:*",