Cache public creator storefront reads in Redis (60s TTL + invalidation)

Commit notes

Profile, storefront config, and published-pack listings are the hot unauthenticated reads; they now serve from a short-TTL Redis cache. Only successful responses are cached (404s propagate uncached), cache failures degrade to Postgres, and mutations (profile update, storefront edit, pack update/publish) invalidate the creator's keys. The 60s TTL bounds staleness for any mutation path that forgets to invalidate.

[private session redacted]