fix(web): bypass data cache for large reference categories

[ntatschner]

Summary

• Next 15 hardcodes a 2 MB per-entry limit on the fetch data cache. The items reference listing weighs ~3.4 MB (and vehicle ~4 MB per memory/wiki-reference-page-sizes.md), so every render calling getCategoryBundle('item') / getCategoryBundle('vehicle') logged Failed to set Next.js data cache for … items over 2MB can not be cached (3441446 bytes) and silently failed the cache write.
• kbCacheOpts now takes the category as an optional arg and returns cache: 'no-store' for the known-large set (LARGE_CATEGORIES = { item, vehicle }). Other categories (weapon, location) keep the 1h revalidate. STARSTATS_DISABLE_FETCH_CACHE=1 still wins globally for the Playwright scenario-isolation path.
• React's request-level fetch dedup still applies — same-URL fetches within a single server render share an upstream call regardless of cache mode. The 3.4 MB inbound transfer per page render touching items is the same cost we were already paying because Next refused to cache it anyway.

If a third category ever crosses 2 MB the symptom is the same log line — add it to LARGE_CATEGORIES.

Test plan

• pnpm --filter web run test:run — 30 tests pass (6 new in reference.test.ts: large-category set membership, revalidate default + small categories, no-store for large categories, STARSTATS_DISABLE_FETCH_CACHE global override)
• pnpm --filter web run typecheck — clean
• pnpm --filter web run lint — no new warnings (3 pre-existing remain in unrelated files)
• Smoke: after merge + platform promote, watch starstats-web logs and confirm the "Failed to set Next.js data cache" warning stops firing for /v1/reference/item and /v1/reference/vehicle requests.