hotfix: remove redis scan invalidation

[sdk-kr]

Summary

• remove Redis SCAN-based reaction cache invalidation from the hot path
• invalidate only exact per-user/per-write reaction keys we can derive
• let short TTL caches expire naturally for the remaining reaction views

Why

• SCAN MATCH on a 300k+ keyspace was driving Redis CPU to 100%
• reaction writes were issuing multiple SCANs per request
• Redis saturation can slow write dedupe/idempotency and contribute to duplicate post/comment submissions

Test plan

• pnpm exec svelte-check (source workspace)
• confirm member-activity-cache no longer calls redis.scan

[github-actions]

Staging 배포 완료

URL: https://dev.damoang.net
이미지: staging-431611f
Static Release: sha-431611f
커밋: 431611f

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