nutrition: use SvelteKit read() for embedding files instead of fs

Replace fragile CWD-based readFileSync path resolution with SvelteKit's
read() + Vite ?url asset imports. This lets the build system manage the
embedding files as hashed immutable assets, fixing ENOENT errors in
production where the working directory didn't match expectations.

package.json

@@ -7,7 +7,6 @@
 		"dev": "vite dev",
 		"prebuild": "bash scripts/subset-emoji-font.sh && pnpm exec vite-node scripts/generate-mystery-verses.ts && pnpm exec vite-node scripts/download-models.ts",
 		"build": "vite build",
-		"postbuild": "mkdir -p dist/data && cp src/lib/data/nutritionEmbeddings.json src/lib/data/blsEmbeddings.json dist/data/",
 		"preview": "vite preview",
 		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
 		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",