#170 · SimpleX Redis-backed rate-limiting + cache (AI throttle parity)

Context

A Redis container is provisioned for the SimpleX bot but unused. Signal rate-limits AI (e.g., 20/hour/user) and caches via Redis.

Acceptance criteria

• [ ] Redis client initialized at startup; AI commands enforce a per-user rate limit.
• [ ] At least one hot path (wiki/embeddings or group list) cached with a sensible TTL.
• [ ] Graceful no-op if Redis is unreachable (don't crash the bot).

Technical hints

• Reuse redis-client.ts / rate-limit helpers in shared-utils.
• SimpleX target: init in src/src/index.ts; apply in the relevant command files.

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