decentraland / comms-message-sfu / 27710900838

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fix: cap incoming packet size and rate limit routed messages (#129)

Incoming LiveKit data packets were decoded and routed with no payload-size
check and no rate limiting, letting a participant amplify load (protobuf
decode + belongsToCommunity + getCommunityMembers + batched fan-out) by
sending many or large packets.

- Add a per-participant token-bucket rate limiter adapter
  (src/adapters/rate-limiter.ts) with lifecycle-managed pruning of idle
  buckets to keep memory bounded.
- In data-received-handler, drop packets larger than MAX_PACKET_SIZE_BYTES
  before decoding and drop packets from participants over their rate limit,
  before any DB lookup or fan-out.
- Record dropped packets via message_delivery_total{outcome=rejected_oversized
  | rate_limited} and document the new env vars in .env.default.

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